LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

GIFT  OK 

Q&  Wtrcis. 

Received  ~fctc<J—  •  l89 

Accession  No.  7  /  7  6~  £   •    Class  No. 


MODERN 
SWITCHBOARDS 

AND  THE  APPLIANCES  USED  THEREON;  TOGETHER 
WITH  AN  HISTORICAL  RESUME'  OF  EARLY  PRAC- 
TICES AND  EXPEDIENTS,  INDICATING  THE  ADVANCE 
RECENTLY  MADE  IN  THIS  CLASS  OF  ELECTRICAL 
APPARATUS;  AND  DATA  ON  APPROVED  METHODS 
OF  CONSTRUCTION 

BY 

ALBERT   B.   HERRICK 


ILLUSTRATED    BY    NUMEROUS    CUTS,    DRAWINGS    AND 
DESIGNS,  ESPECIALLY  PREPARED  FOR  THIS  PUBLICATION 


*J 


THE  CUTTER  ELECTRICAL  AND  MANUFACTURING 
COMPANY,    PHILADELPHIA,    U.S.A.,    MDCCCXCVIII. 


t^: 


COPYRIGHT,  1898 

THE  CUTTER  ELECTRICAL  AND 
MANUFACTURING  COMPANY 


ALL  RIGHTS  RESERVED 


PRICE,    THREE    DOLLARS 


PRESS    OF 

EDWARD    STERN    &    CO.,    INC. 

PHILADELPHIA. 


CONTENTS 


INTRODUCTORY. 

The   advance  of  the  art  of  switchboard  construction.     Old  methods  of  operating.     New 

methods, 7 

- 

CHAPTER  I. 

CIRCUIT  BREAKING  DEVICES.  The  early  methods  of  severing  the  circuit.  Various 
switch  forms.  Slow  break  snap  switches  and  switches  with  auxiliary  contacts.  Physical 
properties  of  contacts.  Types  of  switch  contacts  ;  American,  English  and  German 
types.  Mechanical  and  electrical  properties  of  contact  surfaces, 12 

CHAPTER  II. 

SWITCHBOARD  CONSTRUCTION.  Switchboard  attendance.  Gallery  construction  and 
detail.  Relation  of  switchboards  to  distributing  systems.  Fireproof  construction. 
Exposure.  Framing  and  insulation  of  switchboards.  Method  of  connecting  conductors 
and  bus  bars.  Conductor  losses.  Material  for  electrical  engineering.  Impurities  of  cop- 
per. Dimensions  of  bus  bars.  Weights  and  current  capacities.  Alloys  and  their  con- 
ductivity. Brass  and  other  copper  alloys.  Switchboard  material  and  their  necessary 
properties.  Insulators — wood,  slate,  marble  and  onyx.  Method  of  drilling.  Special 
method  of  switchboard  construction.  Insulating  in  high  tension  switchboards,  ....  21 

CHAPTER  III. 

SWITCHBOARD  APPLIANCES.  Potential  measurements.  Requirements  of  switchboard 
instruments.  Method  of  testing  for  errors.  Checking  methods.  Instrument  movements. 
Solenoid.  Permanent  magnet  type.  Instruments  actuated  by  rise  in  temperature. 
Astatic  voltmeters.  Recording  instruments.  Voltmeters.  Comparative  pressure 
indicators.  Indicating  wattmeters.  Integrating  wattmeters.  Dynamo  galvanometers. 
Dynamo  regulators.  Automatic  regulators,  41 

CHAPTER  IV. 

PROTECTIVE  DEVICES.  Fuses.  Physical  conditions  under  which  fuses  operate.  Con- 
dition where  fuses  are  useful.  Cutter  circuit  breakers — operation  and  reliability.  Types 
of  I-T-E  circuit  breakers.  Lightning  arresters.  Characteristics  of  lightning  discharges. 
Proper  method  of  lightning  protection.  Magnetic  type  of  lightning  arrester.  Types  of 
lightning  arresters.  Non-arcing  lightning  arresters 60 


INTRODUCTORY 

^j=- ji|  HE    evolution  of  the  switchboard  has  necessarily  fol- 
^"—          lowed  the  progress  of  the  various  systems  of  distribu- 


Jtion,  as  a  necessary  adjunct  for  the  controlling  and 
connecting  of  the  different  circuits,  and  it  is  to-day 
necessary  for  the  collection,  distribution  and  control  of 
output  in  any  electric  light,  power  or  railway  system. 

In  order  to  fully  comprehend  the  present  switchboard  practice,  an 
historical  resume  may  be  necessary.  The  earliest  attempt  at  a 
collection  of  apparatus  for  the  purpose  of  controlling  a  distributing 
system  was  at  Menlo  Park,  in  1879,  when  Edison  made  the  first 
commercial  application  of  low-tension  currents  to  a  multiple  arc  dis- 
tributing system.  The  effect  of  assembly  here  was  especially  the 
following  the  diagram  of  connections  with  bare  copper  wires  con- 
necting the  different  plug  devices. 

The  points  of  serviceability  and  utility  came  later  on  in  the  art, 
and  the  necessity  of  measuring  devices  for  the  current  flow  and 
potential,  as  well  as  the  protecting  devices  against  abnormal  flow 
of  current,  soon  asserted  itself. 

The  first  central  station  erected  had  the  apparatus  for  circuit 
and  dynamos  strewn  around  the  four  walls  of  the  station,  regard- 
less of  utility. 

In  1883,  Mr.  Luther  Stierenger,  at  the  Louisville  Exposition, 
designed  the  distribution  circuits  so  that  they  and  their  dependent 
apparatus  were  concentrated  at  one  point.  All  switches,  fuses,  and 
bus  bars  were  brought  together,  and  the  points  of  utility  and  con- 


INTRODUCTORY 

venience  were  realized ;  this  afterward  developed  into  switchboard 
construction. 

The  placement  of  the  switchboard  in  the  older  practice  was  left 
as  one  of  the  last  points  to  be  considered  in  laying  out  a  station, 
but  now  the  proper  position  has  been  found  to  have  such  direct 
bearing  on  the  facility  of  handling  the  apparatus  which  it  controls 
that  the  proper  placement  has  become  a  primary  matter,  and  the 
engineer  has  need  of  all  his  ability  and  judgment  in  considering 
the  conditions  which  determine  the  best  possible  position.  Origi- 
nally wires  secured  to  the  wainscoting  and  plugs  and  crude  instru- 
ments were  connected  in  by  splices.  A  fire  hazard  developed  from 
this  combination;  the  switchboard  was  then  placed  at  a  distance 
from  the  wall,  and  on  a  skeleton  frame,  in  the  construction  of  which 
as  little  wood  as  possible  was  used.  This  sufficiently  reduced  the 
hazard  until  fire-proof  methods  of  construction  were  developed. 
At  first  the  bus  bars  and  their  connecting  cables  were  kept  on  the 
front  of  the  board  until  back  connections  were  necessitated  on  the 
score  of  safety,  space  and  appearance. 

Wood  was  universally  used  for  supporting  instrument  cases, 
regulators  and  equalizers,  as  well  as  for  insulation,  up  to  1889, 
when,  on  account  of  the  high  fire  hazard  placed  on  such  construc- 
tion, slate  and  porcelain  were  substituted  for  wood,  as  the  insulating 
and  supporting  structure. 

The  operation  of  the  early  switchboards  was  comparatively 
simple,  and  the  attendance  and  space  necessary  were  not  considered 
items  to  be  taken  into  account ;  but  on  enlarging  the  field  of  current 
distribution  systems,  careful  designing  had  to  be  done,  in  order  to 
make  the  switchboard  as  compact,  simple  and  easily  operated  as 
possible ;  also,  as  the  current  required  by  the  expanding  system 


INTRODUCTORY 

increased,  new  methods  had  to  be  introduced  in  handling  the  dyna- 
mos and  feeders  of  increased  capacity. 

Fig.  B  shows  the  dynamo  board  of  the  old  Adams  Street  Sta- 
tion, Chicago,  111.,  which  was  an  advanced  type  at  the  time  of  its 
construction,  with  exposed  bus  bars  and  all  apparatus  assembled  on 
a  wooden  facing,  using  wood  for  insulation. 

Fig.  C  shows  the  feeder  board  for  the  same  station,  including 
wooden  frame  equalizers,  which  are  now  relegated  to  the  scrap 
heap  in  nearly  every  station,  as  external  systems  of  distribution 
have  become  more  complex  and  require  economical  methods  to 
obtain  uniform  potential  on  mains,  to  meet  the  varying  demands  on 
the  system. 


THE   FIRST   CIRCUIT    BREAKER 

MADE   BY 
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CIRCUIT  BREAKING  DEVICES 

N  the  evolution  of  circuit  breaking  devices,  it  can 
be  clearly  shown  that  it  is  by  the  slow  process  of 
the  survival  of  the  best  forms,  that  the  present 
stage  of  the  art  has  been  reached. 

The  initial  letter  illustrates  the  primitive  form  of  circuit  rup- 
turing device,  when  the  conductor  itself  is  severed. 

The  switching  devices  that  were  adopted  in  the  early  days  were 
mere  enlargements  of  those  used  in  the  feeble  carrying  current  art. 

The  well-known  plug  came  directly  from  the  telegraph  plug, 
and  the  first  switching  devices  were  derived  from  the  telegraph 
switch,  only  enlarged  to  accommodate  the  greater  volume  of  cur- 
rent flow. 

The  necessity  for  a  mechanical  device,  which  could  open  the 
circuit  without  requiring  the  conductors  to  be 
moved,  was  met  by  having  two  circuit  termi- 
nals end  in  two  insulated  plates,  the  adjacent 
ends   of    which   were   connected    together   by 
the  insertion  of  a  plug,   as  shown  in  Fig.    i. 
The  adoption   of  this  form   of  device  to  the 
heavier  current  art  required  larger  terminals  and   more    area  of 
plug  connection. 

Fig.  2  shows  the  form  commonly  used.  The  functional  weak- 
ness of  this  connection  was  that  the  adjacent  breaking  surfaces 
were  too  near  each  other,  so  that  on  withdrawing  the  plug  the 
arc  followed,  and  could  be  maintained  between  the  terminals. 


12 


CIRCUIT    BREAKING   DEVICES 


FIG.  2 


The  arc  was  extinguished  originally  by  being  blown  out ;  but  as  the 
current  density  ran  up,  other  means  were 
used,  and  it  was  a  familiar  sight  to  see  a  sand- 
box handy,  so  that  if  the  arc  was  too  fierce  to 
be  blown  out,  it  could  be  extinguished  by 
throwing  a  handful  of  sand  on  it.  Two  plugs 
were  also  connected  in  series,  one  to  break  the 
main  circuit,  and  the  other  to  extinguish  the 

resultant  arc. 

\J  The  first   invention   in   switching   mechanisms 

was  the  introduction   of  a  plug  and  flash  plate 

t\  which  were  normally  depressed  below  the  surface 

of  the  plug  switch  base;  but  on  with- 

I    I  A,          drawing  the  plug  this  false  insulation 

plug  and  flash  plate  severed  the  arc  by 
springing  between  the  terminals.  Fig. 
3  shows  the  next  step  where,  by  separa- 
ting the  circuit  terminals,  the  arc  cannot 
hold;  in  this  switch  is  also  shown  the  ele- 
ments  of  the  knife  switch,  which  soon  fol- 
lowed. 

The  circuit  breaking  devices  were,  during 
the  same  period,  following  along  other  lines  FlG  4 

which  were  in  their  inception  a  modification 
of  Fig.  4,  the  strap  key,  and  Fig.  5,  the 
telegraph  key.  Fig.  6  shows  the  earliest 
form  adopted  from  this  origin,  for  heavy 
current-carrying  devices,  and  was  first  made 
in  1879,  for  headboard  switches  for  the  Edison  "Z"  dynamos. 


FIG. 


FIG.  5 


CIRCUIT   BREAKING   DEVICES 


FlG- 


In  this  switch  the  contact  faces  consist  of  two  abutting  surfaces, 

one  being  rigid  on  the  switch  base  and  the  other 
attached  to  a  lever  which  forms  one  terminal  of 
the  circuit,  being  held  positively  in  open  or  shut 
position  by  means  of  a  spring  compressing  a 
stop  in  a  two-way  jockey  plate,  as  shown. 

Fig.  7  shows  another  basic  form,  from  which 
was    probably    developed 
FlG-  6  the  design  of  the  switch 

shown  in  Fig.  8,  but  this  development  took 
place  at  a  later  period. 

From  the  switch  shown  in 
Fig.  3  the  current-carrying 
contact  became  a  flexible 
plate,  bearing  against  a  lever 
which  was  withdrawn,  and 
here  the  advance  was  made 
of  having  a  wiping  contact, 
and  the  arc  was  not  drawn  on  the  current-carrying  surfaces.  Fig. 
8  shows  the  first  mechanical 
form  of  this  switch,  and 
Fig.  9  another  form  where 
the  pivot  forms  one  ter- 
minal. These  switches 
were  next  designed  in  the 
vertical  plane,  in  order  to  reduce  the  room 
occupied,  and  took  the  forms  shown  in 
Figs.  10  and  n.  At  this  time  the  high 
potential  large  current  art  required  another  function  in  switching 


FIG.  8 


FIG.  9 


FIG.  10 


FIG.  it 


CIRCUIT   BREAKING   DEVICES 

devices,  which  was  the  severing  of  the  current  with  great  rapidity, 
in  order  that  the  arc  should 
not  follow  after  the  severing 
member  of  the  switch. 

Fig.  12  shows  the  first 
attempt  to  attain  this  object. 
The  device  consists  of  two 
flexible  contacts  which  are  connected  by  a  conducting  blade,  the 

lower  edge  of  which  has  an  insu- 
lated blade  which,  on  the  withdrawal 
of  the  conducting  blade,  introduces 
an  insulating  medium  between  the 
terminals  of  the  switch.  Also  for 
rapid  removal,  on  withdrawing  the  blade,  a 
spring  is  put  under  compression,  which  snaps 
the  connecting  blade  away  from  the  circuit  ter- 
minals. 

The  next  form  of  switch,  Fig.  13,  is  an  adap- 
tation made  from  Fig.  8,  with  the 
addition  of  a  mechanical  device 
to  throw  the  switch  quickly  by  means  of  compress- 
ing a  spring  when  the  handle  is  thrown  over, 
which  will  withdraw  the  blade  from  its  contacts 
and  snap  it  in  open  position. 

After   these,    numerous    devices   were   adopted, 
having  for  their  function  the  putting  under  tension 
the  blade  as  it  was  withdrawn  from  the  terminals 
or  clips.     Fig.  14  shows  the  first  form,   where  the 
blade  is  first  under  tension  from   a  spring  on  the  handle,  which 

15 


FIG.  12 


FIG    13 


OF   THK 

UNIVERSITY 


CIRCUIT   BREAKING   DEVICES 


FIG   14 


FIG.  15 


then  engages  with  the  blade,  withdraws  and  snaps  on  being 
relieved  from  the  contact  friction.  Fig.  15  is 
another  form  where  the  blade  is  withdrawn  under 
tension  by  means  of  a  spiral 
spring. 

Fig.  1 6  is 
still  another 
form  where 

the  blade  is  snapped  from  contact  by  a 
spring  under  compression.  Fig.  17  has 
an  auxiliary  snapping  tongue,  which 
finally  severs  the  circuit. 

Fig.  1 8  shows  a  snap  switch  where  the 
blade  is  divided  into  two  parts  entering 
one  clip,  the 
upper  half 
leaving  the 
contacts  and 
placing  the 

lower   half  under  tension,    which   is 
withdrawn  with  a  snap. 

Fig.   19  is  a  variation  from   Fig. 
1 8,  in  having  the  snapping  and  mov-  FIG  17 

ing  blades  enter  two  different 
clips,  while  a  tension  is  placed 
between  them  on  withdrawing  the 
blade  fixed  to  the  handle. 

Fig.   20  shows  auxiliary  con- 
tacts composed  of  carbons.     The  purpose  of  these  is  to  effect  the 

16 


FIG.  16 


FIG.  1 8 


CIRCUIT   BREAKING   DEVICES 

same  result  as  that  practically  obtained  by  quickly   snapping  the 
blade   from   its   contact.      This   arrangement   intro- 
duces a  high  resistance  in  the  circuit  before  sever- 
ing it,    and   the   points   of  arcing   at  breaking  the 
circuit  are  between  the  carbons.     The  result 
is  an  arc  of  high  resistance,  which  is  easily 
extinguished.     A  fuse  has  been 
bridged    by     a     switch     blade 
which  will  blow  after  opening  FlG-  I9 

the  switch,  and  in  this  way  protect  the  switch  termi- 
nals.     On    high    inductive    circuits   with   alternating 
currents,   reactive  devices  have  been  placed  between 
the  terminals  of  a  switch  which  opens  the  main  cir- 
cuit,  and  then  the  reactive  device  is  cut  out.       All 
FIG.  20          these  arrangements  have  for  their  object  the  reduction 
in  volume  of  the  main  current  before  finally  opening  the  circuit. 

SWITCH    TERMINALS 

• 

The   positions  of   the   parts   and   members  of   the   switch   are 
largely  a  matter  of  convenience,  but  the  method  of  designing  in 
order  to  decrease  the  drop  through  the  switch 
with  the  least  possible  amount  of  material  is  one 
of  contacts  and  their  physical  properties.     This 
matter  has  been  given  a  great  deal  of  thought, 
and  it  can  be  said  that  there  is  yet  no  standard 
form  of  contact. 

The  Germans,  English  and  Americans  have 

each    evolved    their    own   type,    each    with    its    distinctive    merits. 
Taking  up  the  original  type  of  contact,  which  consists  of  a  rigid 

17 


SWITCH  TERMINALS 


FIG.  22 


FIG.  23 


member  sliding  between  two  surfaces,  the  first  form  brought  out  was 
a  blade  fitted  between  two  rigid  walls  of  metal,  as 
shown  in  Fig.  21.  This  was  used  in  electro- 
plating practices,  where  the  switch  was  not  dete- 
riorated by  arcing  effects.  The  next  step,  Fig.  22, 
was  to  have  one  side  of  the  terminal,  into  which 

the  blade  entered,  flexible,  and 
holding  the  blade  against  a  rigid 
support  in  order  to  allow  a  slight  movement  of 
the  contact,  due  to  inequalities  of  the  contact  sur- 
faces. Fig.  23  shows  where  both  of  these  clip 
surfaces  have  been  made  flexible 
in  order  to  further  increase  the  contact  surfaces 
between  the  terminal  and  its  blade. 

Fig.  24  shows  another  method  of 
securing  the  flexible  contacts  to  the 
terminal  plate.  Fig.  25  shows  the 
same  general  form  of  construction, 
but  more  flexible  in  its  bearing  on  the  contact  sur- 
faces,  and  the  flexible  contacts  soldered  into  grooves 
cut  in  the  terminal  plate.  Fig.  26  is  a  form  used  in 
small-capacity  switches,  where  the  flexibility  of  contact 
y:  is  obtained  by  a  continuous  metal  plate 

fife^.  bent  to  form  both  contact  clips.      Fig. 

ft  27  shows  the  same  result  obtained  by 

k  ^^^L          reversing  the  conditions  found  in  Fig. 
^•^IBl       25,  the  moving  arm,  in  this  case,  being 

Fic-  27  the  flexible  contact  member  and  the  terminal  being 

the  rigid  contact  member.     The  object  of  this  arrangement  was  to 

18 


FIG.  24 


FIG.  26 


SWITCH   TERMINALS 


FIG.  28 


FIG.  29 


reduce  the  drop  on  the  switch,  due  to  the  discontinuous  connection 
between  the  flexible  contact  member  and  the  ter- 
minal.    Fig.  28  shows  a  multiplication  of  the  same 
general  construction  as  Fig.  25,  in  order  to  increase 
the  area  of  the  contact  without 
introducing  the   inflexibility   of 
one  large  moving  switch  blade. 
Fig.  29  is  the  element  from  which  the  Ger- 
man  and    English   types   of  switch  emanated. 
They  consist  of  a  flexible  contact  surface,  bearing  on  a  rigid  ter- 
minal surface  ;  in  this  case  the  contact  is  a  flexible 
brush,  wiping  over  the   terminal. 
This  has  been  reduced  in  heavier 
sizes  of  switches  to   a  number  of 
flexible  fingers,  bearing  against  the 

contact  terminals,  as  shown  in  Fig. 

FIG-  3°  r»-  .LI  i 

30.      .big.  31  shows  the  same  ele- 

ment of  construction,  but  where  the  blade  is  intro- 
duced between  the  rigid  terminals.  Fig.  32  shows 
the  construction  which  effects  the  same  flexibility  between  the  dif- 

ferent fingers  of  two  contact  surfaces,  the  two  sur- 

faces being  in  this  case  the  sepa- 

rate terminals  of  the  circuit. 
Fig-    33   shows  the  recent 

American     improvement      in 

contact    surfaces    where    the 

movable  contact  member  con- 

sists of  a  laminated  surface  of 
a  great  number  of  individual  spring  contacts,  which,  on  their  intro- 

19 


FIG.  31 


SWITCH    TERMINALS 

duction  between  contact  surfaces,  offer  individual  flexible  contact 
points  for  carrying  the  current  from  the  movable  member  to  the  termi- 
nals, and  in  this  way  presenting  a  large  surface  under  compression. 

CONTACT   SURFACES 

The  materials  which  form  the  contacts  should  possess  the  quality 
of  not  mutually  abrading  each  other  when  rubbing  together.  Two 
similar  metals  are  liable  to  bite  and  tear  the  contact  surfaces,  and 
they  should  be  selected  so  as  to  have  different  physical  character- 
istics, in  order  that  they  will  wear  well  together. 

The  conductivity  of  a  contact  surface  is  dependent  upon  three 
values  :  the  pressure  which  they  bear  on  each  other,  the  character 
of  surface  exposed  to  the  conductivity  of  current,  and  the  character 
of  metals  forming  the  contact  areas. 

As  a  conductor,  a  contact  surface  behaves  as  if  it  were  com- 
posed of  a  multitude  of  points  on  a  flexible  warped  surface,  and  as 
the  pressure  is  increased,  more  of  the  points  come  in  contact,  and 
the  pressure  plays  a  more  important  part  in  the  conductivity  of  a 
contact  than  the  area.  With  a  rise  in  temperature  of  the  termi- 
nals, the  actual  drop  between  the  contact  will  fall,  if  there  is  no 
local  potential  due  to  the  metals  in  the  contact  setting  up  a  local 
thermo-electro-motive  force,  or  Peltier  effects. 

In  the  case  of  copper  and  zinc,  and  their  alloys,  there  is  no 
appreciable  thermo  effect,  but  for  lead-aluminium,  lead-iron,  tin- 
aluminium,  tin-iron,  bismuth-iron,  bismuth-aluminium,  in  combi- 
nations, there  is  a  very  appreciable  resistance  over  normal,  due  to 
local  counter  electro-motive  forces ;  the  resistance  of  contact  rises 
rapidly  with  time,  and  all  local  currents  tend  to  depreciate  the  sur- 
faces of  contact  through  which  they  act. 

20 


SWITCHBOARD  CONSTRUCTION. 


OCATING  the  switchboard  is  determined  by  the  relative 
positions  of  the  operating  machinery  in  the  plant.     It  is 
desirable  that  all  points  of  control,  namely,  the  throttle 
of  the  engine,   the   switchboard   and  the   dynamo 
commutators,  be   near  together,    and    so  arranged 
that  they   can  be  easily  reached  by  an  attendant 
without  squeezing  past  fly-wheels  or  belts. 

In  short,  do  not  arrange  your  apparatus  so  as 

to  put  the  attendant  under  any  physical  hazard. 

When  trouble  arises,   it   is   necessary  to  take   care   of  several 

things  at  once,   and  their  close  proximity  to   each   other  renders 

the  attendant  more  eflicient.     This  is 

especially  true  in  isolated  plants.     In 

moderate-size    stations    the    functions 

of  each    attendant   are   less  involved, 

and     the     switchboard     and     genera- 
tors  are    generally   under   one   man's 

care.       In     the    larger     stations     the 

general  practice  is  to  have  one  attend- 
ant whose  only  duty   is  to  take  care 

of    the     switchboard.      The     modern 

tendency,  both   abroad   and  at  home, 

is    to    place    the    switchboard    on    a 

gallery    or    in    an    elevated   position, 

where   the    attendant   has  'a   full    view    of   the   operation    of    the 


FIG.  35 


21 


GALLERY   DESIGN   AND   LOCATION 


PLATE -3*. 


generators  under  his  charge,  and  can  act  promptly  in  a  case  of 
emergency. 

The  following  shows  a  number  of  designs  of  gallery  construc- 
tions ;  also  stairways  leading  to  gallery ;  both  spiral  and  straight. 
Designs  of  railings  are  shown  in  Plate  34;  Fig.  35  shows  a  design  of 
a  gallery  of  cantilever  construction;  Fig.  36  shows  a  double-decked 
switchboard,  reached  by  a  spiral  stairway,  and  Fig.  37  shows  a 

plain  .railing  for 
a  slightly  ele- 
vated gallery. 
Each  case  of  gal- 
lery construction 
is  entirely  de- 
pendent upon 
the  architectural 
arrangement  of 
the  station,  and 
these  illustra- 
tions are  given 
only  to  indicate 
certain  prac- 
tices. In  this 
location  of  the 
switchboard,  if 
the  dynamo 
leads  are  run 
above  the  dyna- 
mo to  an  under- 
ground system, 


FROM  DESIGNS  BY   HERR1CK  &   BURKE. 


22 


SWITCHBOARD    LOCATION 

or  underneath  the  dynamo  to  an  overhead  system  of  distribution, 
extra  copper  in  these  two  cases  is  not  necessary  to  conduct  the 
current  to  the  gallery.  Where  the  current  has  to  be  carried  up 
to  the  gallery  and  back  again,  there  is  considerable  length  of  con- 
ductor used,  only  on  account  of  the  gallery  location. 

Where  the  handling  of  100,000  amperes  is  concerned,  as  in 
some  of  the  larger  three-wire  systems,  where  distribution  is 
underground,  the  indications  are  that  future  practice  will  be  to 
locate  the  bus  bar  in  the  same  plane  as  the  distribution  and  supply 
systems,  and  to  operate  the  switching  mechanism  from  the  gallery 
by  mechanical  or  transmission  methods,  thereby  saving  a  large 
expense  in  conductors  and  waste  of  energy  in  transmission,  there 
being  located  on  the  gallery  only  the  measuring  instruments  and 
regulating  devices,  and  the  levers  to  operate  the  circuit-changing 
switches.  Compressed  air  is  used  at  present  for  mechanically  open- 
ing circuits  at  high  speeds  at  a  distance  from  the  operator. 

In  some  cases,  the  external  distributing  system  will  be  the 
determining  factor  for  the  location  of  the  switchboard,  in  order 

to  have  short  internal  conductors  and 
reduce  internal  losses;  where  the  cur- 
rent flow  is  large,  the  matter  of  conduc- 
tor lengths  becomes  a  very  important 
factor. 

There  is  another  marked  general  ten- 
dency  in    switchboard   construction,  that 
is,  to  make  the  whole  structure  absolutely 
FlG- 3§  fire-proof;    there    is    no    reason    why    a 

central  station  should  contain  any  combustible  material  other  than 
the  necessary  waste  and  oil. 

23 


CONSTRUCTION    DETAILS 

There  is  at  the  command  of  the  electrical  engineer  to-day  fire- 
proof material  for  every  form  of  switchboard  and  insulation,  neces- 
sary in  central  station  construction.  Asbestos  aifords  a  very  good 

fire-proof  covering  for  the  conductors,  and  pre- 
vents them  from  conducting  fire  to  different 
parts  of  the  building;  low-tension  conductors 
may  be  bare,  and  supported  by  porcelain  insu- 
lators (see  Fig.  38)  or  bus  bars  supported  by 
marble,  as  shown  in  Figs.  39  and  40. 
FlG  39  Every  advance  advocated  by  insurance 

inspectors  in  this  direction  is  mutually  important  for  the  central 
station  manager  to  preserve  this  class  of  property  from  destruction 
by  fire,  besides  being  an  economical  investment  in  the  way  of 
obtaining  lower  insurance  rates  on  this  class  of  risks. 

Do  not  place  the  switchboard  under  steam  pipes,  or  have  an 
exposed  window  open  on  the  back  of  the  board.  Do  not  allow 
automatic  sprinklers  to  be  placed  over  the  board,  for  if  they  should 
act,  the  current  leakage  through  the  wet 
surfaces  would  cause  a  far  worse  hazard 
than  could  normally  exist  with  a  properly 
constructed  switchboard. 

The  switchboard  should  be  supported 
away  from  the  wall,  in  order  to  have  the 
back  connections  accessible ;  the  underwri- 
ters'  rules  require  such  placement  in  several  districts.  The  dis- 
tance between  the  wall  and  the  back  of  the  board  has  not  been  suf- 
ficient in  the  larger  boards,  as  there  should  be  three  and  one-half 
feet  in  the  clear  in  order  that  the  attendant  can  properly  work 
behind  the  board,  and  not  make  false  connections  with  his  tools. 


24 


FRAMING 


Wooden  frames,  known  as  the  skeleton  form  of  construction, 
have  been  used  for  the  supporting  of  switch- 
board instruments.  This  step  was  taken  to 
reduce  the  amount  of  combustible  material  used, 
and  to  separate  the  switchboard  from  the  panel- 
ing or  woodwork  of  the  station.  Fig.  41  shows 
method  of  joining  and  making  skeleton  switch- 
boards. 

FlG- 4I  Oak  or  ash  is  the  material  gener- 

ally used.  The  horizontal  slats  are  placed  at  such 
distances  apart  that  the  apparatus  can  be  readily 
secured  to  them.  This  form  of  construction  was  very 
much  in  vogue  some  years  ago,  but,  on  account  of  the 
fire  hazard,  it  was  abandoned  where  switchboard  con- 
struction was  seriously  considered. 
The  next  step  was  to  substitute  slate  for  the  slats, 
and  still  use  the  wooden  vertical  supports,  with 
the  instruments  and  devices  mounted  on  the  slate. 
Later,  I-beams,  channel  bars  or  "L"  iron  were 
substituted  for  the  wood  to  support  the  marble  or 
slate ;  in  this  way  the  space  occupied  by  the  supports 
for  the  board  and  bus  bars  was  much 
less,  and  the  clearances  behind  the  board 
were  more  favorable  to  make  good  connections. 

Figs.  42  and  43  show  methods  of  securing  mar- 
ble or  slate  to  the  verticals. 

Standard  steel  sections  being  used,  the  switch- 
board can  be  readily  erected;  but  the  precaution  to 
have  them  insulated  from  the  building  structure  should  always  be 


FIG.  42 


FIG.  43 


FIG.  44 


FRAMING   AND   CONNECTIONS 

borne  in  mind  where  iron  framework  is  used.  This  can  be  readily 
done  by  supplying  foot-plates  of  marble,  as  shown  in  Fig.  44,  and 
having  the  guys  or  expansion  bolts,  which  stay  it  from  the  wall, 

insulated   by   a   coupling,    as   shown    in 

Fig-  45- 

In  railway,  high  potential,  and  three- 
wire  systems  with  grounded  neutral, 
it  is  very  essential  to  have  the  iron 
framework  carefully  insulated  from  the  building  structure,  in 
order  to  bring  up  the  ground  resistance,  as  well  as  to  prevent  any 
jumping  of  current  or  running  discharges  behind  the  board  to 
ground ;  also  the  hazard  of  injury  to  attendants  working  behind  a 
switchboard  which  is  insulated  from  the  ground  is  greatly  reduced. 

CONNECTIONS 

Methods  of  making  connections  between  conductors  behind  a 
switchboard  are  of  various  kinds,  depending  on  the  form  and  purpose 
of  the  conductor.  These  various  methods  are  connected  together 
and  shown  in  Plate  46;  some  of  them  are  standard,  and  some 
have  inherent  weaknesses  which  have  led  to  their  abandonment. 

The  first  shown  is  the  familiar  wrapped  splice,  which  is  used 
with  bare  conductors,  where  they  are  both  served  with  copper  wire 
and  soldered  together. 

The  second  is  the  sleeve,  where  a  thin  brass  tube  is  slipped  over 
both  ends  to  be  connected  and  soldered. 

The  third  form  is  a  clamp  connection,  where  both  conductors 
are  parallel  and  clamped  together  in  one  connector. 

The  fourth  connection  is  where  the  wire  is  turned  under  the 
head  of  the  bolt  and  screwed  down. 

26 


PLATE  46 


CONNECTIONS 

The  clamp  connection  shown  in  the  fifth  is  the  "V  type, 
where  two  pieces  with  "V  recesses  clamp  the  wire. 

The  sixth  is  an  obsolete  connection,  where  a  sleeve  is  split  and 
provided  with  a  taper  thread  on  the  outside,  over  which  screws  a 
taper  nut,  and  compresses  the  sleeve  over  the  copper  rod.  The 
weakness  in  this  connection  consists  of  the  fact  that  when  the  con- 
ductor heats,  it  expands  and  stretches  the  clamping  nut  so  as  to 
loosen  the  connection.  All  connections  which  have  in  their  incep- 
tion the  surrounding  of  a  solid  conductor  with  a  sleeve  which  is 
not  strong  enough  to  resist  stretching  under  expansion,  will  event- 
ually give  trouble  by  heating. 

The  seventh  shows  the  regular  lug  connection,  and  the  eighth  a 
connection  often  provided  for  in  the  terminals  of  back-connected 
switches;  if  the  stud  screws  into  the  terminal  and  the  nut  locks 
these  together,  the  arrangement  is  satisfactory;  but  if  the  stud 
passes  through  the  switch  with  a  nut  only  on  top,  and  the  bearing 
on  the  bottom  a  small  shoulder,  this  method  of  connecting  will 
eventually  give  trouble. 

The  ninth  form  shows  where  a  threaded  stud  is  secured  to  a  bus 
bar  by  means  of  two  nuts,  which  form  a  good  connection.  Angles 
are  usually  formed  in  bus  bars  by  means  of  bolts;  steel  or  iron  bolts 
should  always  be  used  for  this  purpose. 

The  tenth  form  is  the  method  used  when  a  bus  bar  connects  to 
a  bus  rod. 

The  eleventh  connection  is  when  the  end  of  this  rod  is  cut  to  a 
taper  ol  twenty  degrees,  and  a  female  taper  lug  is  bolted  down  on 
it.  Where  these  surfaces  are  ground  together,  it  makes  a  very 
good  form. 

The  twelfth  shows  the  German  method  of  securing  a  cable  to  a 

29 


CONNECTION   EFFICIENCIES 

lug,  by  forcing  taper  screws  into  the  stranding,  and  in  this  way 
expanding  the  cable  and  securing  contact. 

There  are  a  great  number  of  other  methods  used,  of  connections 
for  special  purposes,  but  not  of  general  application  to  switchboard 
connections. 

We  have  in  the  case  of  a  contact  an  effective  negative  coeffi- 
cient for  temperature ;  we  may  explain  this  in  this  way : 

As  the  contacts  expand,  they  tend  to  present  more  surface  of 
contact,  and  are  under  contact  at  a  higher  pressure  than  when  at 
normal  temperatures.  The  effect  of  the  increased  efficiency  of  a 
joint  at  elevated  temperatures  is  very  clearly  shown  when  the  parts 
in  contact  are  held  by  a  steel  bolt.  Either  brass  or  copper  expands 
faster  than  the  iron  bolt,  and  under  these  conditions  you  can  enor- 
mously increase  the  pressure  on  the  contact  and  decrease  the  losses 
at  this  joint.  The  conductivity  of  the  iron  bolt  is  not  of  as  much 
importance  as  this  increased  pressure  by  unequal  expansion  of  the 
different  parts  of  the  conductor. 

To  take  the  volts  drop  on  a  connection,  and  multiply  it  by  the 
amperes  passing,  will  give  the  watts  at  that  particular  current  den- 
sity ;  but  where  it  is  a  matter  of  contact  surfaces,  the  drop  will  not 
follow  as  quickly  as  a  current  rises.  To  assume  that  this  is  pro- 
portional leads  us  into  very  grave  errors. 

In  specifying  any  system  of  conductors  for  switchboard  and 
operating  devices,  the  losses  should  be  expressed  at  full  load,  in 
volts  drop. 

BUS   CONDUCTORS 

There  has  been  an  erroneous  idea  that  by  laminating  and  allow- 
ing large  radiating  surfaces,  conductors  can  in  this  way  be  kept 

30 


BUS   CONDUCTORS 

cool,  and  consequently  the  losses  reduced ;  some  have  advocated 
forcing  the  density  up  to  as  high  as  three  thousand  amperes  per 
square  inch  for  copper.  The  supposed  gain  is  keeping  the  temper- 
ature down  so  that  the  resistance  will  not  increase,  due  to  the  tem- 
perature coefficient  for  that  conductor;  but  there  are  constant  losses 
in  energy,  which,  if  saved  by  using  better  proportioned  conductors, 
would  pay  a  handsome  interest  on  the  investment  for  the  additional 
copper.  An  example  will  illustrate  this  fallacy  more  forcibly : 

Suppose  we  had  six  thousand  amperes  to  carry  one  thousand 
hours  in  one  year  40  feet.  With  bus  bars  at  a  current  density  of 
eight  hundred  and  fifty  square  mils  per  ampere,  and  using  five 
bus  bars  in  multiple,  2  x  %  inch  x  40  feet.  R=. 0000668.  The 
watts  lost  will  be  2,404  per  hour,  or  2,404  kilowatt  hours  per  year, 
which  if  produced  at  a  cost  of  one  cent  per  kilowatt  hour,  the  loss 
will  cost  $24.04  per  year.  This  bus  bar  weighs  771  pounds,  and 
will  cost,  erected,  approximately  $308.00. 

Take  the  same  case  as  above,  but  using  a  density  of  three  thou- 
sand amperes  per  square  inch,  or  three  hundred  and  thirty  square 
mils  per  ampere,  and  we  will  increase  the  radiating  surface  by 
using  a  bus  bar  2  x  V8  inch  x  40  feet,  which  will  have  a  resistance 
=.0001688.  The  watts  lost  per  hour  will  be  six  thousand,  and  the 
kilowatt  hours  per  year,  six  thousand.  The  cost  of  production  is 
one  cent  per  kilowatt  hour ;  this  will  make  the  lost  cost  $60.00  per 
year.  The  weight  of  the  bus  bar  is  155  pounds,  and  the.  cost  to 
erect  $70.00;  the  difference  in  the  losses  is  $35.96,  and  the  differ- 
ence between  the  two  investments  is  about  $238.00,  or  for  the 
additional  expenditure  of  $238.00,  which  would  be  necessary  in 
order  to  have  the  current  density  850  square  mils  per  ampere,  this 
additional  investment  will  earn  fifteen  per  cent,  by  the  economy  in 


BUS   CONDUCTORS 

waste  energy,  effected  by  this  additional  expenditure  in  copper. 
Again,  in  the  case  cited,  the  laminated  copper  bus,  one-eighth  of  an 
inch  thick,  has  to  dissipate  .33  of  a  watt  per  square  inch  of  surface, 
whereas  the  larger  bus  has  to  take  care  of  only  .2  of  a  watt  per 
square  inch  of  surface  exposed.  In  this  case  the  larger  bus  is 
working  more  advantageously  regarding  ultimate  temperature 
obtained,  and  will  increase  resistance  less,  due  to  this  rise  in  tem- 
perature, which  will  again  be  in  favor  of  the  larger  bus  bar. 

This  example  is  worked  out  for  the  reason  that  a  great  deal  of 
engineering  is  done  on  what  is  known  as  the  least  first  cost  basis, 
regardless  of  what  this  extravagant  economy  costs  in  operation. 
Such  cases  are  more  clearly  demonstrated  by  practical  examples 
than  by  generalities. 

The  materials  of  electrical  engineering,  especially  those  used  for 
conductors,  are  more  often  put  in  by  faith  than  by  test.  The 
station  manager  who  will  have  his  boiler-plate  tested,  which  will 
not  represent  more  than  one-fortieth  of  the  capital  invested  in  the 
plant,  will  neglect  to  have  his  copper  tested,  which  will  represent 
anywhere  from  thirty  to  sixty  per  cent,  of  the  capital  invested  in  the 
plant ;  yet  poor  conductivity  in  the  copper  distributing  system  may 
seriously  affect  the  dividend  which  should  accrue  to  the  installation, 
and  the  current  uselessly  frittered  away  in  heating  the  conductors. 

It  will  be  a  wise  plan,  and  should  always  be  required,  where 
there  is  any  considerable  investment  of  copper  to  be  made,  to  have 
submitted  by  the  manufacturer  a  sample  piece  of  fixed  dimensions, 
delivered  and  tested  for  its  conductivity,  and  if  it  is  to  be  used  for 
overhead  work,  it  should  be  also  tested  for  tensile  strength. 

The  conductivity  of  copper  is  seriously  affected  by  the  presence 
of  other  metals,  even  in  very  small  quantities,  especially  arsenic 


BUS   CONDUCTORS 

and  tin.  The  most  important  impurity  which  will  appear  if  the 
copper  is  not  properly  handled  in  smelting  is  the  sub-oxide  of  cop- 
per. The  brittleness  of  electrolytic  copper  is  generally  due  to  the 
presence  of  copper  hydride  formed  during  deposition.  The 
low  conductivity  of  over-refined  fused  copper  is  due  to  the  pres- 
ence of  carbide  of  copper,  which  is  formed  in  the  presence  of  carbon 
as  soon  as  the  sub-oxide  disappears.  Copper  impurities  can  only 
be  detected  first  by  the  physical  properties  of  the  copper,  and 
second  by  a  chemical  test. 

The  steel  and  iron  manufacturers  fill  specifications  requiring 
fixed  physical  properties  in  their  products — so  should  the  copper 
producer  be  required  to  fill  both  electrical  and  mechanical  condi- 
tions, which  are  so  important  to  the  successful  operation  of  a  plant 
from  a  commercial  standpoint. 

Other  conductors,  such  as  iron,  aluminium,  etc.,  have  been  pro- 
posed, but  in  all  cases  the  conductivity  has  been  so  low  that  the 
mass  to  carry  any  given  current  is  from  seven  to  thirteen  times  that 
for  an  equivalent  copper  bus  bar,  and  this  larger  conductor  requires 
much  more  space  than  can  be  afforded  behind  the  switchboard ;  the 
insulating  expense  and  the  cost  per  unit  of  current  carried  is 
greater  than  with  copper  at  the  present  market  prices. 

The  dimensions  of  bus  bars  are  generally  selected  by  the  cur- 
rent which  they  have  to  carry,  and  the  connections  which  have  to 
be  made  to  them ;  two  copper  busses  bolted  together  wrill  carry 
about  one  hundred  and  eighty  amperes  per  square  inch  of  contact 
section,  and  the  cross-section  carries  approximately  twelve  hundred 
amperes  per  square  inch.  Consequently  the  dimensions  of  the  bus 
selected  should  be  such  that  it  will  present  proper  area  of  contact 
for  connections,  without  making  them  excessively  long. 

33 


BUS    CONDUCTORS 

The  current  which  is  found  in  average  practice,  which  can  be 
carried  economically  by  copper  bus  bars,  is  given  in  the  table 
below;  these  current  densities  are  covered  by  ordinary  central 
station  practices  where  the  load  factor  is  not  greater  than  fifty  per 
cent.  The  resistance  per  foot,  the  area  in  circular  mils  and  square 
mils,  and  the  weight  per  foot  are  given. 

COPPER   BAR   DATA 


SIZE 

AMPERES 

CIRCULAR 
MILS 

SQUARE 
MILS 

OHMS 
PER  FOOT 

WEIGHT 

PER 
FOOT 

i   x  ^  in. 

433 

318310 

25OOOO 

.0000336 

•97 

i^x>4  « 

530 

397290 

3  i  2000 

.0000269 

1.  21 

*y*  x  y\  " 

626 

477465 

375000 

.OOOO223 

i-45 

13^  x  ft  " 

725 

556400 

437000 

.OOOOI92 

1.70 

i^x  ya  « 

676 

596830 

468750 

.0000179 

1.82 

i^  x  #  " 

798 

7l62OO 

562500 

.OOOOI49 

2.18 

13^  x  %  " 

916 

835600 

656250 

.0000128 

2-54 

2   x  %  " 

1035 

954930 

750000 

.OOOOII2 

2.92 

2%xf/  « 

H54 

1074300 

843750 

.OOOOO995 

3-27 

2^  X  X  " 

1500 

I59I550 

1250000 

.OOOOO672 

4.86 

2^  X  %  "        1715 

1989440 

1562500 

.00000537 

6.07 

2    X^  " 

No.  oooo  B.  &  S. 
yz  in.  Round 

K  " 

K  "   " 

j    (i     u 

1222 

257 

305 
426 

560 

861 

1273240 
2II6OO 
25OOOO 
390625 
562500 
IOOOOOO 

IOOOOOO 

.00000840 
.0000505 
.OOOO428 
.OOOO273 
.OOOOI9O 
.OOOOIO7 

3.89 
.64 
.76 
1.18 
1.71 
305 

Bus  bars  are  formed  by  having  the  copper  billet  drawn  through 
graduated  dies.  If  these  dies  are  not  properly  graduated,  or  are 
dull,  the  surface  of  the  copper  becomes  torn  and  reduces  the  use- 


34 


BUS   CONDUCTORS 

fulness  for  bus  bar  work,  as  a  good  connection  cannot  be  made  on 
an  abraded  surface.  If  the  surface  of  the  bus  bar  is  warped  it 
should  be  straightened,  in  order  to  make  a  good  contact.  Specifi- 
cations for  bus  bars  should  be  drawn  so  that  they  can  be  rejected 
for  any  of  the  above  mechanical  imperfections.  Bus  bars  are 
drawn  soft,  medium  or  hard,  as  ordered.  Medium  is  the  bus  bar 
usually  ordered.  Ordinary  tools  and  ordinary  tool  speeds  will 
work  copper  satisfactorily.  If  the  tools  tear  instead  of  cutting  the 
metal,  use  milk  as  a  lubricant,  and  the  cutting  will  be  perfectly 
smooth. 

COMPOSITIONS 

In  any  mixture  of  other  metals  with  copper,  the  resultant  alloy 
will  be  reduced  in  conductivity  below  the  mean  of  the  different 
metals  forming  the  mixture.  There  has  been  no  law  yet  discovered 
between  the  conductivity  of  the  different  metals  and  the  resultant 
alloy,  from  which  the  conductivity  of  the  alloy  can  be  predeter- 
mined. It  will  be  seen  in  the  table  on  following  page  that  the  con- 
ductivity of  these  alloys  is  more  rapidly  reduced  when  any  quan- 
tities of  tin  are  added  to  copper,  than  with  an  equal  portion  of  zinc, 
except  in  the  instance  when  tin  is  present  in  very  small  quantities, 
just  sufficient  to  make  the  metal  flow  into  a  mould ;  this  will  give 
the  highest  conductivity  of  metal  that  casts  readily,  except  in  the 
case  of  one-half  per  cent,  of  silver  and  ninety-nine  and  one-half 
per  cent,  of  copper,  which  gives  a  conductivity  of  eighty-nine 
per  cent. 

No  old  metals  should  be  remelted  where  conductivity  is  required, 
as  they  have  very  low  conductivities,  and  metal  otherwise  good 
may  be  burned  in  the  pot  and  seriously  affect  the  resultant  com- 

35 


COMPOSITIONS 


position.  Brass  is  a  mixture  of  two  parts  copper  and  one  part  zinc, 
and  from  the  peculiar  properties  of  this  mixture,  it  is  probable  that 
there  is  a  chemical  combination  at  this  ratio,  and  not  a  purely 
mechanical  mixture,  as  with  most  alloys.  So-called  cast  copper 


COPPER 
PER  CENT. 

ZINC 
PER  CENT. 

TIN 

PER  CENT. 

CONDUCTIVITY  COM- 
PARED WITH  COP- 
PER AS  100  PER  CENT. 
CONDUCTIVITY 

VALUE  AS  A   CON- 
DUCTOR COMPARED 
WITH  PURE  COPPER 
AT  20  CTS.  PER  LB. 

98.44 

94.49 
88.89 
86.67 
82.54 
75.00 
73-30 
67.74 

oo.oo 

98-59 

93-98 
90.30 

89.70 
88.39 
87.65 
85.09 
16.40 

I.56 

5-51 
II.  II 

r3-33 

17-5° 

25.00 

36.70 
32.26 

100.00 

46.88 
33-32 
25.50 
30.90 
29.20 
22  08 
22.27 
25.40 

27-39 
62.46 
19.68 
12.19 
IO.2I 
12.10 
10.15 
8.82 
12.76 
11-45 

42.22 
59-20 
78.40 
64.60 
68.40 
81.40 
89.80 
78.60 

73-oo 
32.00 
101.60 
164.00 
195.80 
165.20 
197.00 
204.00 
159.80 
1  74.60 

cents 

i  i 

i  i 
i  t 
.1 
it 

it 

it 

u 
Ii 

u 

1  1 
II 
II 
U 

,    I 
II 

1  I 

1.41 
6.02 

9.70 
10.30 

ii.  61 

12.35 
14.91 
83.60 

IOO.OO 

varies  all  the  way  from  eighteen  per  cent,  to  eighty-nine  per  cent, 
conductivity  of  pure  copper,  and  a  number  of  methods  are  used,  as 
well  as  mixtures,  which  will  make  the  copper  flow  into  a  mould 
and  conform  to  the  pattern. 

36 


COMPOSITIONS 

In  switchboard  construction  the  current-carrying  appliances 
should  be  so  designed  that  they  can  be  worked  directly  out  of  pure 
copper  stock ;  do  not  use  cast  metal  where  the  current  densities  are 
high,  and  where  the  economy  of  material  and  labor  is  to  be  con- 
sidered. 

The  bronzes  are  employed  in  special  cases  for  their  mechanical 
properties  rather  than  their  electrical  properties,  as  their  conduc- 
tivities are  low. 

SWITCHBOARD    MATERIAL 

The  actual  surface  on  which  the  switchboard  appliances  are 
assembled  should  have  the  physical  properties  of  possessing 
mechanical  strength,  insulating,  and  be  fire-proof;  besides,  it  is 
necessary  that  it  be  drilled  readily  and  have  a  good  surface  on 
which  to  mount  the  diiferent  appliances,  which  are  combined 
together  to  form  the  switchboard. 

Wood  possesses  the  mechanical  strength  and  insulation  when 
dry,  but  it  is  not  fire-proof.  There  have  beeri  a  number  of  attempts 
made  to  impregnate  the  wood  with  silicate  of  soda,  or  other  fire- 
proof compounds,  or  even  to  paint  it  with  fire-proof  paint,  in  order 
to  make  it  incombustible.  Wood  has  also  been  covered  with 
asbestos  paper,  in  order  to  serve  the  same  purpose,  but  none 
of  these  methods  have  proved  satisfactory. 

The  natural  stones  offer  the  best  material  for  switchboard  sur- 
faces, and,  above  all,  slate  is  the  most  generally  used.  The  insula- 
ting qualities  of  slate  vary  with  diiferent  mines,  and  also  with  dif- 
ferent parts  of  the  same  mine ;  but  generally  speaking,  a  uniform 
color,  gray  or  brown  slate,  without  any  marked  seams  or  veins,  will 
be  found  to  be  a  fair  insulator.  Slates  which  fracture  readily 

37 


SWITCHBOARD   MATERIAL 

along  the  veins,  and  in  which  the  fractured  surface  shows  a  semi- 
metallic  color,  are  always  treacherous  to  use.  Slate  should  have  a 
bright,  laminated  fracture  along  the  plane  of  its  natural  cleavage, 
and  if  it  has  a  dull  fracture,  it  is  very  liable  to  be  too  porous,  and 
will  absorb  moisture,  which  will  reduce  its  insulating  value.  As  a 
rule,  soapstone  is  too  soft  and  fragile  to  be  used  for  switchboard 
purposes,  and  does  not  hold  enameling  well.  Slate  surfaces  are 
treated  with  enamel  paint,  and  different  imitations  of  marble  and 
wood  are  in  this  way  made,  the  enamel  being  burnt  in  and  hardened 
and  polished  to  a  surface. 

Among  the  marbles  every  variety  can  be  found  in  regard  to 
color  and  finish,  but  not  many  of  them  possess  high  insulating 
qualities.  White  Vermont  is  soft  and  fragile,  as  well  as  being  too 
porous  to  exclude  moisture,  and  a  drop  of  oil  will  spoil  a  slab ;  for 
these  reasons,  it  is  very  rarely  used  for  switchboard  purposes. 

The  granites  are  too  hard  to  drill  and  holes  will  drift  when  hard 
spots  are  reached. 

There  are  a  number  of  Tennessee  marbles,  such  as  the  gray  and 
the  champion  pink,  both  of  which  have,  as  a  rule,  high  insulating 
qualities  and  are  easily  worked ;  they  also  make  very  pretty  com- 
binations with  dull  coppered  finished  appliances. 

Of  the  foreign  stones,  Italian  marble  and  Mexican  onyx  make 
very  good  surfaces,  and  as  a  rule  are  good  insulators.  The  former 
is  probably  more  extensively  used  for  switchboard  construction 
than  any  other  marble  in  America. 

To  drill  marbles,,  use  the  slow-speeded  twist  drill ;  there  will  be 
no  trouble  in  drilling  marbles  in  this  way,  if  the  drill  is  not  allowed 
to  choke  with  the  marble  dust,  because  when  this  happens  the  drill 
gets  hot  and  draws  the  temper.  Where  large  holes  are  to  be  cut, 

38 


SWITCH  BOARD    MATERIAL 

the  quickest  way  is  to  use  an  iron  pipe,  the  right  size  outside,  with 
teeth  cut  on  the  lower  edge ;  rotate  this  in  the  drill  chuck  and  feed 
with  emery ;  in  this  way  the  hole  can  be  ground  through  very 
quickly.  When  there  is  trouble  with  the  holes  breaking  out  in  the 
back,  with  large  size  drills,  first  drill  an  eighth  of  an  inch  centre 
hole  and  then  drill  with  a  large  drill  from  both  faces. 

TILE   CONSTRUCTION 

Glazed  tiles  have  been  built  up  as  a  wall,  forming  a  surface  for 
the  switchboard,  the  tiles  being  laid  in  cement,  and  the  holes 
drilled  through  with  hand  drills,  where  required  for  securing  appa- 
ratus; also  cast-iron  frames,  in  which  are  set  porcelain  blocks 
moulded  with  holes,  so  that  apparatus  can  be  thus  secured  and 
insulated. 

SECURING   AND   MOUNTING   SWITCHBOARDS 

Natural  stones,  when  secured  to  wooden  structures,  are  very 
liable  after  a  time  to  crack,  by  the  warpage  of  their  supports.  In 
securing  marble  to  iron  structures,  the  only  precaution  necessary  is 
to  support  the  marble  slab  under  the  securing  bolt,  so  that  the  mar- 
ble is  not  sprung  to  conform  to  the  surface  of  the  iron  work  to 
which  it  is  secured.  Asbestos  washers  between  the  marble  and 
iron,  through  which  the  securing  bolts  pass,  form  a  very  good  bed- 
ding for  marble  slabs,  and  will  support  them  permanently  without 
danger  of  fracture.  Natural  stones  can  be  ground  and  polished  to 
within  one  thirty-second  of  an  inch,  and  when  so  ordered,  all  slabs 
for  one  board  can  be  cut  from  one  block,  so  that  all  veining  can  be 
matched  up,  and  the  color  will  be  uniform.  It  is  necessary,  in 

39 


SECURING   AND   MOUNTING    SWITCHBOARDS 

natural  stones,  to  submit  them  to  a  test;  the  test  usually  made, 
where  only  low  potentials  are  used,  is  by  means  of  a  magneto. 
There  are  two  flat  surfaces  furnished  with  the  leads  to  the  magneto, 
and  these  are  pressed  on  adjacent  surfaces,  or  opposite  surfaces  of 
the  marble  or  stone  to  be  tested ;  if  the  magneto  does  not  ring  up 
with  this  connection,  it  is  passed.  All  that  this  test  indicates  is 
that  there  is  not  a  distinct  metallic  vein  on  the  surface  of  the  slate. 
It  is  the  veins  passing  through  the  slate  which  form  the  conductors 
that  render  the  slate  useless  as  an  insulator.  The  best  way  to  test 
these  veins  is  to  use  a  sharp-pointed  terminal,  and  stab  the  vein  at 
two  points  close  together;  if,  under  this  condition,  you  cannot  ring 
the  magneto,  the  veins  are  probably  non-metallic.  Where  slate  or 
any  veined  material  is  to  be  used  for  high  potential,  it  should  be 
submitted  to  the  actual  potential  stress,  and  should  require  over 
fifty  volts  per  mil  potential  before  it  breaks  down ;  no  marble 
should  be  exposed  to  potentials  over  six  hundred  volts,  without  the 
live  terminals  being  separated  from  the  marble  itself,  by  micanite 
or  other  equivalent  insulator,  as  marbles  and  slates  leak  excessively 
in  moist  weather,  when  they  are  acted  on  directly  by  high  poten- 
tials. This  leaking  heats  the  marble,  disintegrating  it,  and  in  some 
cases  explodes  it. 


40 


SWITCHBOARD  APPLIANCES 

OLTAGE  measurements  should  be  made  with 
greater  precision  than  any  other  electrical 
measurements  in  central  station  work,  espe- 
cially in  low  potential  multiple  arc  distribu- 
ting systems ;  a  constant  potential  is  necessary 
on  the  consumption  circuits,  in  order  to  main- 
tain an  effective  service  and  increase  the  life  of  incandescent  lamps. 
The  conditions  which  surround  measuring  instruments  in 
switchboard  work  must  be  taken  into  consideration  in  their  selec- 
tion. Those  voltmeters  having  magnetic  torque  for  their  indica- 
tion must  be  shielded  from  external  magnetic  influences  when 
near  iron  structures  or  field  magnets.  This  is  generally  taken  care 
of  in  their  design,  either  by  shielding  or  working  under  such 
intense  magnetic  conditions  that  stray  fields  will  not  be  of  suffi- 
cient magnitude  to  introduce  a  commercial  error. 

With  a  varying  voltage,  it  is  essential  that  the  instrument  be 
dead  beat  in  its  action,  and  quickly  respond  to  any  impressed  elec- 
tro-motive force  at  its  terminals. 

The  current  flow  through  a  voltmeter  should  be  as  small  as 
possible,  and  the  temperature  coefficient  of  the  resistance,  in  series 
with  the  moving  system,  should  be  low,  and  should  give  a  negligi- 
ble temperature  error  for  the  instrument  to  be  of  any  real  value. 

An  indicating  instrument  must  be  theoretically  correct  in  prin- 
ciple, accurate  throughout  the  whole  range,  simple  in  construc- 
tion, and  so  proportioned  to  the  work  which  it  has  to  do  that  it 

41 


SWITCHBOARD   APPLIANCES 

will  not  be  eternally  getting  out  of  order,  and  will  stay  in  correct 
calibration. 

To  check  up  the  accuracy  of  voltmeters,  the  temperature  error 
is  found  by  checking  two  voltmeters  against  each  other  when  both 
of  them  are  cold.  Then  place  the  voltmeter  across  the  potential 
at  which  it  operates  for  a  number  of  hours,  until  its  temperature 
has  attained  a  maximum.  Again  check  these  two  voltmeters,  the 
cold  against  the  hot  voltmeter,  and  if  the  readings  now  differ  from 
each  other  more  than  one  per  cent.,  the  voltmeter  should  be  rejected. 

Another  source  of  error  in  voltmeters  is  due  to  pivot  friction, 
which  is  caused  by  the  pivot  wearing  against  the  jewel  bearing  and 
abrading  the  surface,  and  increasing  the  friction  between  these  two 
surfaces ;  this  error  should  not  be  found  in  new  instruments,  as  it 
is  one  which  increases  with  the  ageing  of  the  instrument.  In 
order  to  keep  this  friction  as  low  as  possible,  the  moving  system 
should  be  light,  and  in  order  to  test  friction  errors,  the  instrument 
should  be  moved  quickly,  in  order  to  oscillate  the  index  hand — 
note  whether  the  hand  always  comes  back  and  registers  with  the 
zero  mark — current  should  be  applied  to  the  instrument,  and  dif- 
ferent parts  of  the  scale  tested  in  the  same  way.  The  important 
parts  of  the  scale  where  friction  is  found  largest  are  near  the  standard 
readings,  where  it  is  continually  used.  The  voltmeters  should 
always  be  tested  for  the  friction  error  in  the  same  position  in  which 
they  are  used. 

Means  are  generally  provided  on  the  switchboards  for  checking 
up  the  different  voltmeters  against  each  other,  by  means  of  plugs 
and  a  pressure  switch.  This  should  be  done  at  stated  intervals,  in 
order  to  maintain  the  accuracy  of  these  instruments,  which  are  so 
important  to  the  proper  operation  of  the  system. 

42 


SWITCHBOARD   APPLIANCES 

For  alternating  currents,  the  voltmeter  should  be  calibrated  at 
the  same  frequency  as  that  on  which  it  is  used.  In  some  types  of 
voltmeters  a  change  of  frequency  introduces  a  considerable  error  in 
alternating  current  instruments ;  especially  where  they  are  applied 
to  circuits  having  a  large  power  factor,  they  should  be  carefully 
checked  for  errors. 

INSTRUMENT    MOVEMENTS 

The  different  principles  employed  in  the  movements  of  electrical 
instruments  can,  as  a  rule,  be  used  for  both  volt  and  current  meas- 
urements. The  magnetizing  force,  in  the  case  of  the  voltmeter, 
is  supplied  with  a  great  number  of  turns  of  fine  wire,  and,  in  the 
case  of  the  ammeter,  is  supplied  with  a  few  turns  of  coarse  wire. 

The  oldest  type  of  a  measuring  instrument  was  a  permanent 
magnet  pivoted  over  a  conductor,  which  magnet  was  deflected  by 
currents  passing  through  the  conductor,  and  these  deflections  were 
calibrated. 

The  movements  of  commercial  instruments,  as  now  used  for 
switchboard  work  and  commercial  measurements,  are  only  those 
which  will  be  hereafter  described . 

The  solenoid  type,  in  which  an  iron  core  is 
sucked  into  convolutions,  through  which  the  cur- 
rent circulates,  has  a  pointer  attached  to  the  core, 
and  these  deflections  are  calibrated.  Fig.  47 
shows  an  instrument  employing  the  solenoid 
principle;  in  this  case,  the  core  is  supported  on 
a  knife  edge,  counterbalanced  by  the  pointer  FlG- 47 

and    an    adjustable    weight,    and    can    be    calibrated    to    give    a 
fairly    uniform    scale    for    equal    increments    of    current.       This 

43 


FIG.  48 


INSTRUMENT    MOVEMENTS 

design  is  one  which  is  used  by  the  Brush  Company  on  their  arc 
circuits. 

Fig.  48  shows  another  form  of  solenoid  type;  in  this  case  the 

solenoid  is  circular  and  concentric  to 
the  curve  core  which  swings  around 
the  axis  of  support,  in  response  to  cur- 
rent changes. 

By  properly  balancing  this  system 
by  weights,  a  fairly  uniform  scale  can 
be  secured,  or,  for  special  purposes,  the 
scale  can  be  expanded  at  any  point 
desired.  This  movement  was  used  by 
the  Edison  Company. 

These  two  movements  are  specially 
useful  for  current  indications;  they  have  an  inherent  error  in 
measuring  direct  current,  due  to  the  iron  core  not  responding 
readily  to  slight  changes  of  current,  which  makes  an  increased 
reading  lower  than  it  should  be  and  a  decreased  reading  higher 
than  it  should  be.  This  magnetic  lag  is  called  "hysteresis,"  and 
where  there  is  any  mass  of  iron  employed  in  the  moving  system 
the  accuracy  is  not  sufficient  for  volt  indications,  except  where 
alternating  currents  are  measured,  and  hysteresis  is,  under  this 
condition,  not  an  appreciable  error,  but  in  this  case,  the  precaution 
must  be  taken  to  laminate  the  core,  so  that  local  currents  will  not 
be  induced  in  it. 

Both  of  the  systems  above  described  are  naturally  heavy  in 
their  construction,  so  that  the  coefficient  of  friction  of  the  instru- 
ment is  large,  and  gives  an  error  which  is  practically  identical 
with  hysteresis. 


44 


INSTRUMENT  MOVEMENTS 


FIG.  49 


Fig.   49  shows  still  another  instrument  of  the  solenoid  type, 
which  is  used  specially  for  alternating  current  work,  being  provided 
with  a  laminated  core.     This  movement  is 
used  by  the  Westinghouse  Company. 

The  perfecting  of  devices  for  the  accu- 
rate commercial  measurements  of  electrical 
currents  and  potentials  is  due  to  the  untir- 
ing efforts  of  Mr.  Edward  Weston,  who 
undertook,  in  1880,  to  seriously  develop  for 
the  electrical  industries  instruments  by 
which  the  electrical  quantities  involved  in 
electrical  engineering  could  be  accurately 
determined.  After  having  experimented 
over  the  whole  field  of  the  possible  forms  of 
instruments,  he  determined  on  the  type  of 
instrument  shown  in  Fig.  50,  believing  it  to  embody  the  best  possible 
principles  for  the  measuring  systems  of  commercial  instruments. 
This  type  is  applicable  to  the  measurement  of  direct  currents;  the 

measuring  coil  consists  of  a  number  of 
turns  of  fine  wire,  wound  on  a  rectangular 
form,  and  this  coil  rotates  in  a  concentric 
annular  space,  through  which  passes  a 
permanent  magnetic  field.  When  current 
enters  this  coil,  it  tends  to  deflect  it  from 
a  fixed  position,  which  is  reacted  by  dif- 
ferential springs;  in  this  way  deflections 
can  be  obtained,  which  are  proportional  to  the  current  flowing. 

"A"  represents  the  internal  iron  core;  "B"  the  moving  coil; 
UC'    the  springs,  and  "D"  the  pointer. 


FIG.  50 


45 


INSTRUMENT   MOVEMENTS 

Where  this  instrument  is  used  as  a  voltmeter,  it  has  resistance 
in  series  with  the  moving  coil.  When  used  as  an  ammeter,  it 
measures  the  difference  of  potential  across  a  shunt,  which  differ- 
ence varies  with  the  current  flowing.  These  instruments  are  made 
in  a  number  of  forms  for  switchboard  work — the  round  dial  type 
for  isolated  plants,  illuminated  dial  type  for  central  station  work, 
and  the  edgewise  type  for  heavy  current 
work.  All  these  are  shielded  by  being 
closed  in  iron  boxes,  which  form  the  case. 
Fig.  51  shows  another  instrument  hav- 
ing the  elements  of  a  moving  system  rota- 
ting in  a  permanent  magnetic  field,  this 
movement  being  restrained  by  springs 

which  also  carry  the  current  into  the  moving  systems.  The  instru- 
ment shown  in  this  figure  is  known  as  the  Kennelly  Ammeter, 
manufactured  by  the  Edison  Manufacturing  Company.  This  instru- 
ment consists  of  a  flat  permanent  horseshoe  magnet  of  semi-circu- 
lar shape,  with  its  poles  brought  out  into  semi-circles,  and  separated 

about  one-sixteenth  of  an  inch.  In  this 
narrow  air-gap,  and  working  in  a  strong 
magnetic  field,  is  the  disc  armature  "A." 
The  windings  are  laid  radially  and  symmet- 
rically over  the  upper  surface  of  the  disc, 
and  when  the  current  passes  through  these 
radial  lines,  a  magnetic  pull  is  set  up  in  the 

plane  of  the  disc,  which  causes  the  armature  to  turn  ;  the  deflections 
are  proportional  to  the  current  flowing  through  the  system. 

Fig.  52  shows  another  method  by  which  currents  are  measured 
by  indirect  means,  due  to  the  expansion  of  the  conductor  on  being 

46 


INSTRUMENT    MOVEMENTS 

heated  by  the  current  passing  through  it  and  the  expansion  and 
contraction  of  this  conductor  being  multiplied  and  actuating  a 
pointer,  which  indications  are  calibrated.  This  figure  shows  several 
strands  of  wire,  through  which  the  current  to  be  measured  passes, 
one  strand  of  which  actuates  the  multiplying  device,  to  which  is 
attached  the  pointer.  A  disc  is  attached  to  the  moving  system, 
which  enters  a  semi-circular  air-tight  box,  and  acts  as  an  air  dash- 
pot,  which  reduces  the  oscillation  of  the  meter  and  makes  it 
approximately  dead  beat.  This  instrument  is  known  as  the  Hoyt 
hot  wire  type. 

The  Cardew  type  of  instrument  has  the  conductor  wound 
around  the  spindle  of  the  indicating  hand,  and  rotates  this  around 
as  it  expands  or  contracts;  this  movement  is  again  calibrated. 
These  instruments  have  special  uses  for  shipboard  work,  as  they 
are  not  affected  in  their  indications  by  any  external  movement; 
twisted  strips  of  different  metals  and  spiral  springs  used  torsion- 
ally  have  been  used  for  the  moving  devices  of 
measuring  instruments. 

Fig.  53  shows  what  is  known  as  the  Wirt 
type,  and  consists  of  a  magnetic  field  which 
is  unsymmetrical  to  the  moving  iron  system. 
The  current  is  so  disposed  around  the  moving 
system  that  very  little  iron  is  used,  and  the 

r    1  r     i  Fir"  53 

hysteretic  error,  by  careful  treatment  of  the  iron, 
is  reduced  to  a  negligible  value.  As  the  current  flows  through  the 
loop  surrounding  the  system,  the  iron  tends  to  include  a  greater 
number  of  lines  of  force,  and  this  moving  effort  is  counteracted  by 
weights  or  springs,  so  that  the  deflections  are  proportional  to  the 
current  flowing.  Where  this  system  is  used  for  a  voltmeter,  a 

47 


INSTRUMENT   MOVEMENTS 

number  of  turns  wound  on  an  elliptical  spool,  and  the  moving  sys- 
tem placed  concentrically  to  one  of  the  curved  ends,  makes  this 
form  adaptable  to  volt  indications.  Hoffmann  &  Braum,  Thomson  - 
Houston  and  others  use  variations  of  the  same  principle  for 
indicating  movements. 

ASTATIC    VOLTMETERS 

With  high  potentials  there  exists  sufficient  attraction  between 
surfaces  of  dissimilar  potentials   so   that  a  moving  system  can  be 

operated  by  these  surface  charges. 

Fig.  54  shows  a  type,  originally  designed  by 
Sir  William  Thomson,  in  which  a  moving  vane 
enters  between  two  charged  surfaces;  this  sys- 
tem is  pivoted  and  provided  with  adjustable 
weights,  so  that  voltages  can  be  read  up  to  any 
potential  which  is  only  limited  by  the  striking 
distance  between  the  charged  plates.  This  in- 
strument requires  no  flow  of  current  for  the 
indications,  and  the  scale  is  not  proportional. 
Other  arrangements  of  the  same  principle  have  been  made,  one 
by  Mr.  Kennelly,  where  the  system  is  suspended  and  consists  of  a 
horizontal  vane,  which  carries  vertical  circular  sec- 
tors of  aluminum,  which  rotate  in  grooves  formed 
by  curved  brass  plates.  Current  is  carried  into  a 
moving  vane  by  a  bi-filar  suspension.  When  these 
adjacent  surfaces  are  charged,  they  tend  to  rotate 
the  vane  proportional  to  the  charging  potentials.  FIG.  55 

This  last  arrangement,  on  account  of  the  fibre  suspension,  is  hardly 
adaptable  to  switchboard  construction.  See  Fig.  55  for  details. 


FIG.  54 


48 


ASTATIC    VOLTMETERS 


FIG.  56 


The  permanent  magnet  type  of  instruments  is  not  suitable  for 
the  measurement  of  alternating  currents.  Mr.  Weston  devised  the 
instrument  shown  in  Fig.  56,  which  has,  in 
common  with  his  permanent  magnet  type  of 
instrument,  a  rotating  coil  on  which  is 
wound  the  convolutions  carrying  the  cur- 
rent to  be  measured,  and  the  current  is 
carried  into  the  moving  system  by  spiral 
springs.  The  magnetic  field  in  which  this 
system  rotates  is  also  formed  by  the  current 
to  be  measured,  and  consists  of  two  hollow  helixes  which  enclose 
the  moving  system.  There  is  no  iron  in  this  instrument,  and  it  is 
not  affected  in  its  readings  by  changes  in  frequency.  The  oscilla- 
tions of  the  meter  can  be  damped  by  a  brake  which  is  depressed  on 
pushing  down  the  contact  key.  This  instrument  does  not  give  a 
proportional  scale,  but  one  that  is  expanded  in  the  middle. 

RECORDING   VOLTMETERS 

In  order  that  a  permanent  record  may  be 
kept  of  the  variation  of  voltage  on  any  system 
of  potential,  it  is  important  that  a  visual  con- 
tinuous record  be  kept  of  the  potential,  and 
there  are  several  instruments  on  the  market 
for  this  purpose. 

The  one  shown  in  Fig.  57  consists  of  a 
voltmeter  movement  of  the  solenoid  type,  in 
which  the  plunger  is  supported  on  springs, 
and  has  an  index  extension,  on  the  end  of  which  is  a  pen,  by 
means  of  which  a  line  of  aniline  ink  can  be  traced  on  a  dial. 


FlC.  57 


49 


RECORDING  VOLTMETERS 

This  dial  is  moved  around  at  a  uniform  rate  by  clockwork,  and  the 
variations  of  voltage  are  in  this  way  registered  permanently. 

The  Richard  Brothers'  indicator  records  in  the  same  way  as  the 
above-described  Bristol  indicator,  but  the  actuating  mechanism  con- 
sists of  an  iron  vane  attracted  to  the  poles  of  an  electro-magnet,  and 
the  pointer  carrying  the  aniline  ink  is  attached  to  this  system. 

VOLTMETER    RELAYS 

In  order  to  control  voltages  where  variable  speeds  are  delivered 
to  the  dynamos,  such  as  water-power  or  gas  engines,  it  is  necessary 
that  an  automatic  method  be  used  to  regulate  the  generator  thus 
driven,  as  compounding  will  not  affect  regulation  for  variable 
speeds. 

A  voltmeter  relay  is  used  for  the  purpose  of  actuating  the  rheostat 
which  controls  the  field  circuits.  There  are  a  number  of  methods 
by  which  this  relay  is  operated,  but  generally  by  the  solenoid  and 
plunger  principle,  the  solenoid  being  wound  with  fine  wire,  which 
is  placed  across  the  potential  to  be  controlled.  The  plunger  is 
restrained  by  a  calibrated  spring,  and  makes  connection  with  one 
contact  when  the  voltage  is  high,  and  with  another  contact  when 
the  voltage  is  low.  A  relay  can  be  constructed  so  as  to  regulate 
within  one-half  of  a  volt. 

The  circuit  thus  controlled  by  the  plunger  may  operate  through 
the  means  of  a  motor  or  electro-magnet;  the  arm  of  the  rheostat, 
cutting  in  or  out  resistance  in  the  field  circuit,  maintains,  in  this 
way,  a  constant  potential  at  the  brushes  of  the  generator.  Such 
relays  are  also  used  to  light  signal  lamps  on  the  switchboard,  to  call 
the  attention  of  the  attendant  to  the  fluctuation  of  voltage  from  the 
fixed  standard. 

5° 


VOLTMETER   RELAYS 

The  central  station  in  Paris,  France,  has  its  potential  output 
almost  entirely  operated  by  automatic  devices,  which  are  controlled 
by  automatic  relays. 

COMPARATIVE   PRESSURE   INDICATORS 

In  feeder  distribution  where  the  network  of  mains  are  supplied 
by  feeders  whose  terminal  pressure  should  be  the  same  throughout 
the  system,  the  pressure  wires  are  brought  back  from  the  feeder 
ends  and  can  be  directly  placed  across  the  voltmeter  and  the 
potential  measured,  or  the  difference  of  potential  may  be  compared 
against  the  selected  standard  feeder,  by  means  of  a  comparative 
pressure  indicator.  The  construction  of  this  indicator  is  one  having 
a  permanent  magnet  needle  pivoted,  and  is  actuated  by  one  solenoid 
across  the  standard  feeder  and  one  solenoid  across  the  feeder  pres- 
sure, to  which  it  is  connected ;  the  effect  on  the  magnetic  system  is 
differential,  and  the  potential  read  on  the  instrument  is  the  differ- 
ence of  potential  that  exists  at  the  terminal  of  the  measured  feeder 
from  that  of  the  potential  at  the  terminal  of  the  standard  feeder. 

INDICATING  WATTMETERS 

In  order  to  determine  the  power  on  any  electrical  circuit,  it  is 
necessary  to  multiply  the  current  flowing  by  the 
volts  pressure.  An  instrument  which  records  this 
product  is  shown  in  Fig.  58.  The  main  current 
flows  around  the  moving  system,  and  the  potential 
on  this  circuit  flows  through  the  moving  system,  and 
the  inter-reaction  of  these  two  forces  is  calibrated, 
according  to  their  mutual  forces,  directly  into  a  scale  FlG- 

of  watts  which  is  the  power  element  of  the  circuit  being  measured. 

51 


INDICATING   WATTMETERS 

This  instrument  has  special  uses  in  the  low  potential  systems, 
where  the  load  curve  in  amperes  does  not  indicate  the  power  out- 
put of  the  station;  for  as  the  current  consumption  rises,  the  external 
distribution  losses  increase,  which  is  compensated  for  by  raising 
the  bus  pressure,  so  that  an  indicating  wattmeter  is  the  only  indi- 
cation of  output  which,  when  plotted  on  a  curve,  is  comparable  to 
the  station's  economical  performance. 

INTEGRATING  WATTMETERS 

In  any  variable  load  delivery,  to  multiply  the  current  by  the 
volts  for  a  limited  number  of  observations  during  the  day,  in  order 
to  determine  the  watt  output,  never  leads  to  reliable  results  being 
obtained,  unless,  of  course,  the  plant  happens  to  be  operating  under 
constant  load.  For  these  measurements  instruments  of  the  inte- 
grating type  have  been  devised,  which  operate  by  the  combined 
effect  of  the  current  flow  and  potential  difference ;  their  rotations 
vary  with  the  product  of  these  two  forces. 

Their  construction  is,  in  all  cases,  quite  similar  to  an  ordinary 
shunt  motor,  the  conditions  of  field  and  armature  being  reversed. 
The  field  is  in  series  with  the  load;  the  armature,  which  is  of  high 
resistance  and  generally  of  Siemens'  construction,  with  a  commutator 
of  a  few  segments,  is  placed  "in  shunt  across  the  line,"  the  shunt 
being  taken  off  beyond  the  field  coils.  An  outside  resistance  is  placed 
in  this  shunt  circuit,  to  reduce  the  current  in  the  armature  to  the 
necessary  small  quantity,  and  to  prevent  any  appreciable  waste 
across  the  line.  Also,  a  few  shunt  turns  in  some  types  act  accumu- 
latr  .ly  with  the  series  turns,  to  compensate  for  friction  of  armature 
rotation. 

52 


INTEGRATING   WATTMETERS 

Motor  meters,  as  a  class,  rotate  far  more  rapidly  than  is 
allowable  in  practice.  It  has  been  necessary,  therefore,  to 
introduce  a  "drag"  or  resistance  to  rotation,  to  slow  the  meter 
to  a  reasonable  speed.  This  has  been  done  in  several  ways, 
and  perhaps  the  most  common  method  is  to  attach  a  number  of 
air  fans  to  the  shaft.  These  are  quite  largely  used,  and  with  fair 
success. 

The  resistance  of  an  air  fan  to  rotation  is  approximately  pro- 
portional to  the  square  of  the  speed ;  therefore,  this  device  is  only 
fitted  for  combination  with  such  meters  as  have  a  torque  increasing 
with  the  square  of  the  current.  However,  since  the  torque  of  such 
meters  does  not  quite  reach  the  square,  the  retarding  effect 
increases  rather  too  rapidly,  and  has  a  tendency,  although  not 
always  pronounced,  to  cause  the  speed  of  the  meter  to  fall  off  pro- 
portionately on  high  loads. 

Another  method  of  "drag,"  which  has  been  used  with  some 
success,  is  the  rotation  of  a  small  fan  in  a  liquid — a  method 
perhaps  rather  better  than  the  previous  one,  since  resistance  to 
rotation  falls  below  the  square  of  the  speed  when  the  liquid 
itself  begins  to  rotate.  Much  depends  in  this  case  upon  the 

shape    of    the    receptacle    containing    the 
fluid. 

A  third  method  consists  in  rotating  a 
small  inefficient  dynamo,  generally  a  mere 
disc  turning  between  permanent  or  electro- 
magnets. This  resistance  is  of  course 
directly  proportional  to  the  speed,  and  there- 
fore to  the  torque.  Applying  this  "drag" 
friction  solves  the  principal  difficulty  to  contend  with. 

53 


INTEGRATING  WATTMETERS 

Fig.  59  shows  the  type  of  Thomson  integrating  wattmeter,  which 
is  adapted  for  both  alternating  and  direct  watt  indications,  and 
made  especially  for  switchboard  work.  The  main  current  enters 
the  meter  through  the  "U'  turn  of  copper,  which  produces  the 
field  in  which  the  armature  rotates.  The  potential  across  the 
armature  varies  with  the  voltage,  and  the  damping  effect  is  pro- 
duced by  a  copper  disc  rotating  in  a  permanent  magnetic  field. 
The  summation  of  the  revolutions  are  recorded  on  a  dial. 

Fig.  60  shows  an  integrating  meter  which  is  specially  used  to 
measure  alternating  current.  This  meter  is  essentially  an  induc- 
tion meter.  The  entire  current  to  be  measured  passes  through  the 
primary,  and  an  alternating  field  of  force  is  developed 
in  the  direction  of  the  axis  of  that  coil.  At  the  same 
time  an  alternating  current  is  induced  into  the  second- 
ary, and  this  induced  current  develops  another  field  of 
force  in  the  direction  of  the  axis  of  the  second  coil,  and 
therefore  at  an  angle  to  the  primary,  which  produces  a  FlG  6o 
resultant  field,  which  is  constantly  shifting;  this  field  acts  on  a 
disc,  and  the  rotations  are  calibrated  to  correspond  with  the  cur- 
rents flowing,  and  the  indications  on  the  dial  will  be  practically 
ampere  hours.  The  retarding  devices  are  air  vanes. 

DYNAMO    GALVANOMETERS 

In  the  control  of  dynamos,  so  that  they  may  be  thrown  into 
service  together,  a  means  must  be  provided  so  that  it  is  known 
when  the  potential  of  the  generator  is  the  same  as  that  of  the  sys- 
tem on  which  it  is  to  be  thrown. 

In  small  switchboards,  a  voltmeter  switch  is  provided  so  that  it 
can  be  connected  across  the  terminals  of  the  dynamo,  and  its 

54 


DYNAMO    GALVANOMETERS 

potential  adjusted  until  it  is  the  same  as  the  system  to  which  it  is 
to  be  connected.  For  this  purpose,  in  the  older  central  station 
practice,  dynamo  galvanometers  were  used  which  were  connected 
across  one  pole  of  the  dynamo  switch,  the  other  pole  being  closed ; 
when  the  dynamo  is  at  the  same  potential  the  galvanometer  reads 
zero  and  the  machine  can  be  thrown  in  on  the  circuit. 

Another  zero  method  which  is  used  for  this  purpose  consists  of 
a  differential  galvanometer,  one  winding  of  which  is  placed  across 
the  bus  potential  and  the  other  across  the  open  dynamo  switch. 
When  the  potential  on  both  windings  is  equal,  the  hand  stands  at 
zero,  and  the  potential  of  the  machine  is  right  for  throwing  in. 

The  incipient  objection  to  a  zero  instrument  for  this  purpose  is 
that  it  gives  the  same  indications  for  no  current  as  it  does  for  the 
proper  adjustment  of  the  generator;  this  has  led  to  mistakes  being 
made  by  the  switchboard  attendants,  which  has  resulted  in  these 
methods  being  abandoned. 

Now,  each  generator  is  provided  with  a  small  direct  reading 
voltmeter,  which  is  calibrated  in  volts  and  is  provided  with  a  small 
pilot  switch,  where  there  are  several  potentials  used,  so  that  the 
voltmeter  switch  will  indicate  the  proper  positions  in  which  to 
throw  the  main  dynamo  switches  when  the  dynamo  potential  is 
equal  to  the  bus  potential. 

DYNAMO    REGULATORS 

The  regulation  of  dynamos  requires  a  variation  of  the  current 
strength  flowing  through  the  field  circuits,  in  order  that  they  may 
be  thrown  into  service,  and  also  that  the  loads  may  be  properly 
divided  between  the  generator  when  working  in  multiple  arc,  and 
the  proper  potential  maintained  on  the  consumption  circuits.  In 

55 


DYNAMO    REGULATORS 


shunt  dynamos  their  output  is  varied  by  a  resistance  in  series  with 
the  shunt  field,  which  resistance  can  be  varied  to  increase  or 
decrease  the  current  flowing  through  the  field  circuit.  The 
mechanical  device  used  for  varying  this  field  circuit  primarily  con- 
sists of  a  continuous  resistance,  from  which  taps  are  taken  at 
various  points  and  brought  to  contact  blocks,  over  which  the  con- 
tact arm  traverses,  thus  cutting  out  or  in  resistance  in  this  circuit. 

The  ordinary  form  is  shown  in  Fig.  61,  which  consists  of  a  cir- 
cle of  segments ;  the  current  is  introduced  through  the  pivot  of  the 
lever,  and  thence  to  contact  buttons,  and  through 
the  resistance  to  the  other  terminal  of  the  regula- 
tor. The  fault  with  this  device,  as  usually  connec- 
ted, is  that  if  the  lever  contact  leaves  the  contact 
buttons  the  field  circuit  is  open;  if  this  happens 
when  the  machine  which  is  controlled  is  working 
in  multiple  with  others,  serious  damage  may 
result.  Again,  in  large  generators  many  thousand  volts  may  be 
induced  in  the  field  coils  on  the  rupture  of  the  field  circuit,  tending 
to  break  down  the  field  insulation.  For  this  reason  the  permanent 
connection  should  be  made  in  all  such  regulators  from  the  point 
"A"  to  "B,"  so  that  the  field  circuit  is  always  continuously 
through  the  regulator,  even  if  the  lever  is  detached. 

In  any  case  where  a  field  circuit  of  a  generator  over  50  K.  W. 
is  broken,  this  should  always  be  done  slowly,  and  the  arc  drawn  in 
order  that  a  partial  circuit  is  maintained  through  the  arc,  so  as  to 
prevent  the  discharge  of  the  field  from  rising  to  abnormal  potential. 
In  general,  the  field  switches  are  provided  with  field  circuit  con- 
tacts, and  on  withdrawing  the  switch  it  enters  another  set  of  con- 
tacts, which  throws  a  non-inductive  resistance  across  the  field 


FIG.  61 


DYNAMO    REGULATORS 

terminals,  so  that  when  the  field  circuit  is  broken  the  discharged 
potential  is  suppressed. 

The  Siemens-Halske  Company  use  a  carbon  auxiliary  contact 
device,  which  allows  the  field  circuit  to  be  gradually  broken 
between  carbon  points  automatically,  and  suppresses  in  this  way  a 
sudden  surging  of  dangerous  pressure  from  the  field  discharges. 

There  has  been  a  tendency  for  small  units  especially,  to  make 
the  dynamo  regulator  compact.  This,  in  itself,  is  a  very  good 
feature;  but  with  the  same  watts  lost  as  the  size  decreases,  the  tem- 
perature which  the  regulator  attains,  increases  and  uses  the  wire 
nearer  its  fusing  temperature,  practically  results  in  too  many  break- 
downs. 

A  larger  factor  of  safety  should  be  made  in  dynamo  regulators, 
and  much  more  than  has  been  allowed  in  the  past.  A  limiting 
temperature  of  ninety  degrees  Centigrade  for  enamel  or  grid  con- 
struction, and  fifty  degrees  Centigrade  for  open  spiral  coil  construc- 
tion, should  not  be  exceeded.  This  latter  form  of  construction  has 
been  used  largely  in  central  station  work,  simply  because  the  factor 
of  safety  has  not  been  sufficient  in  other  types  of  regulators. 

The  cost  of  a  regulator  does  not  exceed  three  per  cent,  of  the 
cost  of  the  generator  it  controls  in  units,  of  the  size  of  generator 
used  in  central  station  work.  To  increase  the  factor  of  safety  of 
the  regulator  strengthens  the  weakest  part  of  the  regulating  system 
and  greatly  insures  reliability  of  service. 

In  regard  to  the  total  resistance  of  a  regulator,  this  should  be 
such  that  the  dynamos'  potential  can  be  reduced  below  the  normal 
at  no  load,  when  separately  excited  at  normal  potential.  This  is 
an  important  point,  for  a  number  of  manufacturers  obtain  their 
rheostat  data  from  tests  on  generators  which  admit  of  their  being 

57 


DYNAMO    REGULATORS 


self-excited,  and  with  this  connection  it  obviously  takes  much  less 
resistance  to  control  the  generator  than  when  separately  excited. 
In  units  from  one  hundred  kilowatts  up,  the  field  currents  become 
of  considerable  magnitude,  and  the  regulators  to  control  them  have 

to  be  of  special  construction  in  order  to  properly 
carry  and  control  these  currents.  The  contacts 
and  the  connections  are  larger,  and  generally 
switchboards  employing  units  of  this  size  neces- 
sitate compactness;  consequently  the  dial  form 
of  regulator  is  not  suitable. 

Fig.  62  shows  a  regulator  in  which  the  con- 
tact clips  are  arranged  in  two  parallel  staggered 
steps  with  a  sliding  contact  bridging  them, 
which  contact  is  moved  by  a  pinion  in  the 
contact  head  meshing  into  a  rack  on  the  side 
of  the  regulator. 
There  is  also  another  form,  in  which  the  steps  are  arranged 
around  in  two  parallel  quadrants,  and  so  staggered  that  eighty 
changes  of  resistance  can  be  effected  by  moving  the 
regulator  arm  through  forty  degrees.  Both  of  the 
above  regulators  are  connected  to  their  resistance  in 
what  is  known  as  a  loop  connection,  which,  in  effect, 
is  the  same  as  drawing  a  contact  along  two  legs  of  a 
U-shaped  resistance,  and  in  both  regulators  the 
moving  of  the  contact  upward  increases  the  potential 
or  load  on  the  machine. 

In  the  quadrant  type  of  regulator,  it  is  also  neces- 
sary to  open  the  field  circuit,  and  to  prevent  this  being  opened 
accidentally  when  the   machine   is  in   operation,   an   interlocking 

58 


FIG.  62 


FIG.  63 


DYNAMO    REGULATORS 

device  is  used,  which  prevents  the  field  switch  being  withdrawn  or 
thrown  in  unless  the  regulating  lever  is  at  the  lowest  point  (see 
Fig.  63). 

AUTOMATIC    FIELD    REGULATORS 

Where  dynamos  are  driven  at  a  variable  speed,  the  shunt  field 
has  to  be  brought  up  for  a  drop  in  speed,  and  down  for  a  rise 
in  speed. 

There  are  several  automatic  regulators  which  can  assist  regula- 
tion considerably,  if  the  variations  are  not  too  sudden.  They 
employ  an  automatic  relay  which  is  operated  by  a  given  change  in 
voltage,  which,  in  turn,  closes  a  circuit  through  a  solenoid  or  motor, 
which  actuates  the  contact  lever  to  throw  in  or  take  out  resistance ; 
in  this  way  compensation  is  made  for  speed  variations.  The  con- 
tact lever  is  usually  provided  with  a  dash-pot  or  other  equivalent 
damping  device  to  prevent  hunting  of  the  regulator  and  surging 
in  the  electro-motive  force  of  the  generator  controlled.  Compound- 
ing will  not  take  care  of  speed  variations  in  a  dynamo. 


59 


PROTECTIVE  DEVICES 

ROTECTION  from  abnormal  flows  of  cur- 
rent, in  a  circuit  which  has  a  limited  current- 
carrying  capacity,  is  necessary  for  the  safety 
of  the  system  and  the  structure  which  con- 
tains it. 

In  any  electrical  distribution,  there  is  a 
fixed  consumption  circuit,  and  the  conductors 
are  proportioned  to  the  current  supplied,  and 

will  take  care  of  all  normal  demands  with  a  predetermined  loss. 
However,  as  the  conductor  system  depends  upon  insulation  to  keep 
the  current  in  the  conductors  themselves,  and  to  limit  the  current 
in  quantity  by  the  consumption  devices  in  that  circuit,  if  the  insu- 
lation fails  or  the  current  demand  becomes  excessive,  this  circuit 
then  should  be  automatically  severed. 

The  proper  method  to  be  employed  for  the  protection  of  such 
circuits  depends  on  the  potential  of  the  circuit,  the  current  supply 
methods,  and  the  character  of  apparatus  to  be  protected,  and  the 
different  devices  which  are  used  for  the  purpose  of  protecting  cir- 
cuits each  have  their  own  special  sphere  of  usefulness. 

FUSES 

Much  has  been  written  on  this  matter,  and  there  is  hardly 
another  "example  in  electrical  engineering  where  so  much  has  been 
done  in  the  laboratory  without  comprehending  the  true  practical 
function  of  the  device  and  its  inherent  limitations. 

60 


FUSES 

The  rating  of  the  fuse  is  the  determination  of  six  variables  :— 
its  specific  resistance,  its  temperature  coefficient,  the  cooling  effect 
of  the  terminals,  the  conditions  for  dissipating  heat  by  convection 
and  radiation,  the  specific  heat  of  the  metal,  and  the  latent  heat 
required  by  the  fuse  metal  for  its  volatilization;  the  two  last 
have  more  direct  bearing  on  the  time  element  of  the  fuse  than  on 
its  rating.  In  use,  the  aging  effects  on  the  fuse  are  found  to  be  the 
oxidization  due  to  the  elevated  temperature  at  which  it  is  used, 
and  also  its  molecular  stability  changing  under  the  variations  of 
temperature. 

These  variables  have  all  to  be  considered  in  the  rating  of  a  fuse ; 
and  to  make  a  fuse  for  a  specific  number  of  amperes,  in  order  that 
it  can  be  connected  with  any  kind  of  terminals,  be  blown  in  any 
position  and  at  any  external  temperature  or  condition  of  moisture, 
has  obviously  led  to  the  present  doubt  as  to  the  accuracy  of  the 
fuse.  In  fact,  any  fuse  can  be  so  arranged  that  by  conditions 
external  to  the  fuse  itself,  it  can  be  made  to  carry  continuously  a 
current  flow  one  hundred  per  cent,  above  its  rating. 

The  usefulness  of  the  fuse  as  an  automatic  device  is  only  real- 
ized when  adapted  to  that  duty  for  which  it  was  originally  intended, 
namely,  to  protect  the  conductor  system  from  injury.  The  fuse 
being  made  the  weakest  point  in  the  circuit,  it  should  have  such 
reliability  as  to  not  allow  such  an  excessive  current  to  flow  through 
the  conductor,  so  as  not  to  create  a  fire  hazard  or  injure  the  insula- 
tion of  the  conductor.  It  would  be  much  more  practical  to  num- 
ber fuses  to  correspond  with  the  size  of  wire  which  they  are 
designed  to  protect,  and  be  of  such  rating  that  they  will  blow 
between  those  currents  above  which  the  wire  is  allowed  normally 
to  carry,  and  below  that  current  which  will  injure  the  conductor  or 

61 


FUSES 

its  insulation,  and  there  is  plenty  of  margin  between  these  two 
current  capacities  to  allow  for  all  the  variables  which  will  alter  the 
current-carrying  capacity  of  the  fuse. 

To  send  out  a  fuse  marked  to  blow  at  a  given  number  of 
amperes,  or  even  fuse  wire  sent  on  spools,  rated  in  amperes  has  led 
to  the  belief  that  they  could  be  accurately  calibrated ;  but  without 
fixing  the  conditions  of  the  length  and  terminals  and  holder,  they 
in  practice  do  not  give  reliable  service.  It  is  a  physical  impossi- 
bility to  be  sure  that  results  can  be  reached  in  practice  between 
one  hundred  per  cent,  of  each  other;  yet  to  protect  the  conductors 
from  excessive  heating,  due  to  abnormal  current  flow,  is  within 
their  legitimate  use ;  but  to  suppose  that  by  overloading  a  fuse  ten 
or  twenty  per  cent,  that  it  will  blow,  is  not  within  the  original 
intention  or  the  present  possibilities  of  this  device. 

Determining  the  sphere  of  usefulness  of  the  fuse  is  a  simple 
question  of  cause  and  effect.  On  circuits  of  high  or  low  potential, 
not  carrying  currents  over  thirty  amperes  in  most  instances,  an 
effective  service  can  be  rendered  by  the  fuse,  and  it  will  operate 
quickly  enough  to  fulfil  the  ordinary  demand  of  a  circuit- rupturing 
device.  At  these  capacities  the  resistance  of  the  fuse  can  be  con- 
siderable without  undue  loss,  as  the  heating  of  the  fuse  increases  as 
the  square  of  the  current  flowing  multiplied  by  the  resistance  of 
the  fuse ;  also  the  thermal  conduction  of  the  heat  and  the  areas  of 
radiation  are  low,  and  the  mass  of  metal  to  be  volatilized  small ;  so 
fuses  up  to  these  capacities  can  be  given  a  fairly  reliable  rating,  and 
are  in  some  measure  independent  of  the  variables,  which  assume 
large  proportions  in  fuses  at  higher  current-carrying  capacities. 

On  low  potential  systems  fuses  are  used  extensively  for  the 
reason  that  they  can  be  of  such  capacity  that  they  will  not  operate 

62 


FUSES 

unless  there  is  an  extraordinary  demand  on  the  system,  for  the 
current  in  these  systems  rises  to  an  abnormal  amount  when  the 
conductors  are  either  grounded  or  crossed ;  but  their  use  is  being 
abandoned  in  the  large  network  of  underground  mains  from  cen- 
tral lighting  stations  and  copper  strips  substituted.  It  is  consid- 
ered better  practice  to-day  to  maintain  current  when  a  short-circuit 
occurs  on  these  mains  until  it  is  burned  out,  rather  than  hazard  the 
continuity  of  the  service  due  to  fuses  blowing. 

Fuses  should  not  be  considered  as  a  reliable  protective  device, 
as  it  is  a  very  important  fact  that,  when  the  time  arises  for  their 
action,  it  should  be  prompt;  for  it  is  evident  that,  by  continuing 
the  condition  of  short-circuit,  excessive  strains  may  be  brought  on 
the  current-generating  machinery  and  engine,  as  this  strain  has  to 
be  maintained  long  enough  to  raise  the  temperature  of  the  fuse  to 
the  melting  point  and  then  supply  sufficient  energy  to  volatilize 
the  fuse  before  the  circuit  is  ruptured.  Modern  practice  indicates 
that  more  than  the  external  circuit  itself  has  to  be  considered,  as 
the  reaction  on  the  generating  system,  which  is  supplying  the  ser- 
vice, becomes  a  very  important  factor.  In  compound  generators, 
where  the  effect  of  sudden  rise  in  current  demand  on  the  gene- 
rators is  accumulative,  it  makes  it  very  necessary  that  the  cur- 
rent be  severed  quickly,  as  soon  as  it  has  reached  a  fixed  value. 

In  modern  central  station  practice  the  promptness  of  action 
of  an  automatic  circuit -rupturing  device  becomes  its  most 
important  function,  where  protection  is  to  be  afforded  to  the 
generating  apparatus.  The  distributing  system,  however,  can 
be  subjected  to  a  much  greater  variation  in  current  flow,  and 
stand  the  strain  for  a  longer  period;  so  that  in  this  class 
of  protection  the  time  element  of  circuit-breaking  is  not  so 

63 


FUSES 

important.  The  fuse  generally  consists  of  a  metal  having  a  low 
fusing  point,  the  combination  of  tin,  lead  and  bismuth  being  those 
usually  employed  in  the  alloy.  These  are  soldered  to  hard  end 
terminals,  usually  of  copper,  the  terminals  having  ears  provided  so 
that  they  may  be  clamped  to  the  contact  blocks.  Fuses  are  also 
made  for  high  potential  service  of  a  number  of  strands  of  fuse  wire, 
each  enclosed  with  a  rubber  tube.  Also  copper  is  used  in  the  form 
of  wire,  but  it  has  a  very  large  time  constant,  and  has  to  be 
maintained  at  considerable  temperature  if  operated  near  its  rated 
capacity.  Copper  fuses  have  also  been  used,  wound  in  the  form  of 
a  spiral,  so  that  in  rupturing  the  circuit  the  arc  is  drawn  in  a  mag- 
netic field,  due  to  the  convolutions  of  the  fuse,  and  in  this  way 
extinguished.  In  order  to  reduce  the  radiating  effect,  fuses  are 
enclosed  in  glass  tubes,  and  in  some  cases  are  surrounded  by  a 
chemical  which  combines  with  the  fuse  metal  itself  on  reaching  a 
fixed  temperature,  and  in  this  way  reducing  the  resultant  arc  on 
the  breaking  of  the  circuit.  In  this  same  class  are  also  fulminate 
fuses,  which  have,  in  close  proximity  to  the  fuse,  a  fulminate  which 
explodes  when  the  fuse  reaches  a  certain  temperature,  and  in  this 
way  ruptures  the  circuit. 


AUTOMATIC    CIRCUIT    BREAKERS 

A  great  many  methods  and  devices  have  been  employed  for  the 
purpose  of  mechanically  rupturing  a  circuit  by  its  own  effect,  after 
it  has  reached  a  predetermined  point.  The  magnetic  effect  of  the 
current  itself  is  generally  used  to  actuate  an  armature,  which  in 
turn  releases  the  switching  device.  Expansion  of  conductors  has 
also  been  used  to  disconnect  the  circuit,  but  the  time  constant  of 

64 


AUTOMATIC   CIRCUIT   BREAKERS 

any  heating  effect,  caused  by  the  current  itself,  is  far  too  slow  to 
be  effective,  as  is  shown  in  the  case  of  fuses. 

In  order  to  accomplish  the  result  desired  in  a  circuit  breaker, 
the  time  between  which  the  abnormal  current  rises  in  the  cir- 
cuit to  be  controlled  and  the  actual  opening  of  the  circuit 
should  be  as  short  as  possible;  in  other  words,  the  time  of  open- 
ing should  become  less  and  less  in  proportion  as  the  strength  of 
flow  increases,  for  the  reason  that  the  circuit  which  it  controls 
may  be  short-circuited,  and  this  current  can  quickly  assume 
large  proportions.  It  is  important  that  any  circuit-rupturing 
device  should  act  as  quickly  as  possible  after  the  current  has 
commenced  to  rise  above  the  set  value,  so  that  the  rupturing 
device  can  break  the  circuit  before  the  current  flow  has  attained 
such  volume  as  would  be  destructive  to  any  rupturing  contact; 
and  the  quicker  the  circuit  breaker  acts,  the  greater  the 
advantage  to  both  the  generating  apparatus  and  the  distribut- 
ing system. 

The  actual  breaking  of  the  circuit  should  be  performed  posi- 
tively and  with  certainty ;  yet  to  sever  a  high  potential  would 
necessitate  drawing  an  arc  which  would  seriously  interfere  with 
the  proper  action  of  the  contact  surfaces.  Provision  must  be  made 
so  that  this  arc  will  occur  where  it  cannot  damage  the  current- 
carrying  parts  of  the  breaking  mechanism. 


THE   CUTTER   CIRCUIT    BREAKER 

This   circuit   breaker   is   the   successful   issue  of  many  years' 
extensive  research  into  the  problem  of  automatically  severing  of 

65 


THE   CUTTER   CIRCUIT   BREAKER 

electric  circuits,  and  the  perfected  device  as  we  have  it  to-day  is 
the  outcome  of  tests  made  under  practical  conditions,  rather  than 
the  product  of  laboratory  experiment. 

Plate  "C'  shows  the  construction  of  this  circuit  breaker  in 
side  view  and  in  part  section.  The  main  current  circulates  around 
the  solonoidal  coil  "B"  and  tends  to  draw  into  the  solenoid  the 
movable  plunger  "C."  The  initial  position  of  this  plunger  in  the 
solonoid  is  determined  by  the  adjusting  screw  "M."  When  the 
current  is  sufficient  to  overcome  the  weight  of  the  plunger  it  is 
drawn  into  the  coil  with  constantly  increasing  velocity,  due  to 
intensified  magnetic  action,  as  the  polar  distance  or  air  space  is 
decreased.  When  nearing  the  upward  limit  of  its  travel,  having 
acquired  a  high  momentum,  it  impinges  upon  the  trigger  UN' 
through  the  medium  of  the  push  pin  "  E."  The  immediate  result 
of  this  is  the  release  of  the  switch  arm  by  the  displacement  of  the 
retaining  catch  "  F."  The  upper  projection  "H"  of  the  trigger 
u  N '  is  thrust  against  the  striker  plate  "  K,"  thereby  utilizing 
the  energy  of  the  current  to  start  the  movement  of  the  switch  arm. 
This  movement  is  intensified  and  sustained  beyond  the  point  of 
final  rupture  between  the  switch  contacts  by  the  thrust  of  the 
spring  "O,"  which  is  released  from  compression  by  the  initial 
action  of  the  trigger.  Thus  the  contact  arm  is  thrown  away  from 
the  contact  terminal,  and  the  circuit  is  opened. 

Plate  "  D  "  shows  the  disposition  of  the  main  contacts  and  of 
the  auxiliary  carbon  contacts  through  which  the  current  flows  after 
the  copper  switch  plates  have  been  severed.  Upon  these  carbon 
surfaces  the  current  is  finally  ruptured.  By  this  arrangement  the 
metallic  contacts  are  preserved  from  the  deleterious  effects  of  an 
arc,  the  circuit  being  finally  ruptured  between  the  auxiliary  carbon 

66 


-U  I-T-E 

Circuit  Breakers 

CUTTER  ELECTRICAL 
AND  MFG. 


PLATE  C 


HJ2  SANSOM  ST. 
PHILADELPHIA,  U.S.A. 


THE   CUTTER   CIRCUIT   BREAKER 


contacts.  The  efficiency  of  carbon  for  a  final  break  is  due  to  the 
fact  that  the  vapor  resultant  upon  the  formation  of  an  arc  has  a 
high  resistance,  and,  owing  to  the  refractory  nature  of  this  sub- 
stance, but  a  relatively  small  volume  is  volatilized  by  the  action  of 
the  arc,  which,  in  addition,  introduces  into  the  partially  severed  cir- 
cuit a  counter  electro- 
O)  motive  force,  approxi- 

mating forty  volts. 

Among  the  impor- 
tant results  attained 
by  the  development 
of  the  Cutter  circuit 
breaker  are  : — First, 
the  great  reduction  in 
the  time  elapsing 
between  the  occur- 
rence of  the  excessive 
current  and  its  final 
interruption.  In  the 
event  of  a  fault  or 
derangement  in  the  distributing  system  the  current  tends  to  rise 
with  extreme  rapidity;  the  prompt  interruption  of  the  circuit, 
breaking  the  current  before  it  has  attained  its  full  abnormal  value, 
thus  becomes  a  matter  of  the  greatest  importance.  Some  recent 
tests  of  these  instruments  show  that  the  circuit  breaker  responded 
wathin  five  one-hundredths  of  a  second  after  the  occurrence  of  a 
short-circuit,  and  the  current  which  would  normally  reach  two 
hundred  amperes  was  severed  before  eighty  amperes  flowed  through 
the  circuit  breaker,  showing  that  with  normal  inductance  of  gener- 

69 


PLATE  D 


PLATE  E 
I-T-E  CIRCUIT  BREAKER 

STANDARD  SWITCHBOARD  TVPE.      SINGLE  POLE.     5  TO  200  AMPERES 


THE   CUTTER    CIRCUIT   BREAKER 

ating  apparatus  the  circuit  breaker  acted  more  quickly  than  the 
generators  could  respond  to  the  demand ;  consequently,  abundant 
protection  was  afforded. 

The  responsiveness  of  the  device  upon  the  occurrence  of  a 
gradual  overload  is  no  less  marked.  Friction  and  the  conforma- 

o 

tion  of  the  magnetic  circuit,  if  not  properly  taken  care  of  in  the 
design  of  a  circuit  breaker,  will  allow  the  current  to  creep 
beyond  the  point  at  which  the  device  is  adjusted  to  operate  before 
the  force  of  the  solenoid  is  sufficient  to  actuate  the  plunger.  In 
this  instrument  the  plunger  is  free  to  move  without  appreciable 
friction,  and,  being  worked  far  below  the  point  of  its  magnetic 
saturation,  it  is  extremely  sensitive  to  current  changes.  This, 
in  combination  with  the  structural  features  alluded  to,  insures 
a  positiveness  of  action  which  altogether  precludes  the  possi- 
bility of  "floating,"  as  it  has  been  termed.  It  may  be  hardly 
necessary  to  add  that  the  circuit  breaker  is  a  very  efficient  pro- 
tection against  damage  by  lightning. 

Plate  "E"  shows  the  standard  switchboard  type  of  the  Cutter 
circuit  breaker,  of  from  five  to  two  hundred  amperes  capacity,  in 
an  open  position;  Plate  UF,"  a  larger  instrument  of  the  same  type, 
of  from  two  hundred  to  twelve  hundred  and  fifty  amperes  capacity, 
closed,  while  Plate  UGV  shows  a  still  larger  circuit  breaker  of 
standard  switchboard  type,  single  pole,  of  from  fifteen  hundred 
to  three  thousand  amperes.  All  of  these  are  intended  for  direct 
current  only  and  are  single  pole,  for  use  on  circuits  of  six  hundred 
volts  or  less,  the  long,  clear  break  making  them  peculiarly  adapted 
to  the  severe  conditions  incident  upon  street  railway  work.  They 
are  equally  suited  for  lighting  and  power  circuits,  up  to  and 
including  six  hundred  volts. 

7* 


PLATE  F 

I-T-E  CIRCUIT  BREAKER 
STANDARD  SWITCHBOARD  TYPE.     SINGLE  POLE.     200  TO  1,250  AMPERES 


PLATE  G 

I-T-E  CIRCUIT  BREAKER 

STANDARD  SWITCHBOARD  TYPE.     SINGLE  POLE.     1,500  TO  3,000  AMPERES 


THE   CUTTER   CIRCUIT   BREAKER 

Plate  "Hv  is  a  double  pole  circuit  breaker,  of  a  capacity  of 
from  thirty  to  two  hundred  amperes,  for  voltages  of  two  hundred 
and  fifty  or  less.  As  illustrated,  it  is  intended  for  front  connec- 
tions, making  it  suitable  for  panel  board  work.  For  use  on 
switchboards  it  would  be  used  with  back  connections. 

Plate  "!'•'  is  a  larger  instrument  of  the  same  type,  having  a 
capacity  of  from  two  hundred  to  fifteen  hundred  amperes,  double 
pole,  for  use  upon  circuits  having  a  voltage  of  two  hundred  and 
fifty  or  less,  equally  adapted  for  lighting  or  power. 

Plate  "Jv  represents  a  circuit  breaker  of  from  two  hundred  to 
six  hundred  amperes  capacity,  double  pole,  double  coil.  Not  only 
is  this  instrument  designed  to  open  both  sides  of  the  circuit,  but, 
having  two  coils,  it  will  be  operated  upon  the  occurrence  of  an 
overload  upon  either  side  as  well  as  by  an  overload  affecting  both 
sides  of  the  line,  thereby  insuring  absolute  protection  of  the  circuit 
under  any  and  all  conditions. 

Plate  UK"  represents  a  type  of  instrument  especially  designed 
to  meet  the  severe  condition  of  opening  an  alternating  current 
circuit  of  two  thousand  volts  or  less.  It  is  made  in  single  pole 
only,  and  has  a  clean,  wide  double  break  of  ten  inches.  In  this 
instrument  the  coils  of  the  smaller  sizes  are  wound  with  covered 
magnet  wire,  and  in  the  larger  sizes  the  coils  are  made  of  open, 
bare  rectangular  copper.  This  type  of  instrument  is  made  up  to 
a  capacity  of  two  hundred  amperes. 

We  have  in  the  foregoing  treated  of  the  Cutter  circuit  breaker 
of  an  overload  type  only.  With  but  a  small  increase  in  the  size, 
and  without  in  any  way  affecting  the  simplicity  of  the  overload 
instrument,  an  underload  function  may  be  added.  A  principle 
analogous  to  that  which  insures  certainty  of  action  in  the  overload 

74 


PLATE  H 

I-T-E  CIRCUIT  BREAKER 
MIDGET  SR.  TYPE.     DOUBLE  POLE.     30  TO  200  AMPERES 


PLATK  I 

I-T-E  CIRCUIT  BREAKER 
STANDARD  SWITCHBOARD  TVPK.     DOUBLE  POLE.     250  TO  1,500  AMPERES 


PLATE  J 

I-T-E  CIRCUIT  BREAKER 
500  AMPERE.     DOUBLE  POLE.     DOUBLE  COIL 


PLATE  K 

I-T-E  CIRCUIT  BREAKER 

ALTERNATING  CURRENT  TYPE  FOR  HIGH  VOLTAGE.     SINGLE  POLE  ONLY 

5  TO  200  AMPERES 


PLATE  L 
I-T-E  CIRCUIT  BREAKER 

DIRECT  CURRENT,  no,  220  AND  500  VOLTS.     5  TO  25  AMPERES 


PLATE  M 
I-T-E  CIRCUIT  BREAKER 

DIRECT  CURRENT,  EITHER  SINGLE  OR  DOUBLE  POLE.     4,000  TO  8,000  AMPERES 


THE   CUTTER   CIRCUIT   BREAKER 

is  made  use  of  in  the  underload,  the  actuation  of  the  trigger  upon 
the  occurrence  of  the  underload  being  effected  by  the  blow  of  an 
armature  moving  under  spring  pressure.  It  will  be  seen  that 
whether  the  cause  of  operation  be  an  underload,  a  "sneak  current," 
or  a  heavy  short-circuit,  the  trigger  will  be  acted  upon  with  a  ham- 
mer blow,  and  never,  in  any  case,  without  a  free  preliminary 
movement  of  the  actuating  body. 

The  underload  device  is  made  in  two  forms,  one  of  which, 
operating  only  upon  the  interruption  of  the  current  supply,  is 
especially  suited  for  motor  protection,  while  the  second  form, 
which  operates  upon  the  occurrence  of  a  predetermined  minimum 
flow,  is  peculiarly  adapted  for  use  in  connection  with  storage 
batteries. 

Plate  "L"  shows  an  overload  circuit  breaker  having  the  under- 
load function  added.  The  type  shown  is  intended  for  direct  cur- 
rents of  from  five  to  twenty-five  amperes,  single  pole.  This  form 
is  regarded  as  the  best  for  storage  battery  protection. 

Plate  UM."  This  type  of  instrument  is  specially  designed  for 
circuits  of  very  large  capacity,  either  single  or  double  pole.  The 
construction  is  such  that  the  current  is  carried  through  laminated 
contacts  in  series  with  the  actuating  coil  of  the  instrument.  The 
main  break  is  between  the  laminated  contacts,  and  is  followed  almost 
simultaneously  by  the  auxiliary  break,  which  is  in  shunt  with  the 
main  contacts,  and  is  protected  by  a  final  carbon  break  of  ample 
capacity.  All  the  features  which  have  made  the  smaller  types  so 
succesvsful  are  preserved  in  this  device,  while  the  arrangement  of 
the  laminated  contacts  and  the  general  design  are  so  accurately 
proportioned  that  the  circuit  breaker  can  be  set  with  no  greater 
effort  than  is  required  in  closing  a  circuit  breaker  of  fifty  amperes. 

Si 


PLATE  N 

I-T-E  CIRCUIT  BREAKER 
OVERLOAD  AND  "No  VOLTAGE."     5  TO  25  AMPERES 


THE   CUTTER   CIRCUIT    BREAKER 

Plate  "N'  shows  an  overload  circuit  breaker  having  a  "no 
voltage  v  function  added.  This  type  is  intended  for  direct  current 
of  from  five  to  twenty-five  amperes,  and  is  regarded  as  best  for 
motor  protection.  They  are  made  for  one  hundred  and  ten,  two 
hundred  and  twenty,  and  also  five  hundred  volts. 

Plate  "O."  This  instrument  has  been  specially  designed  for 
use  in  connection  with  Edison  three-wire  currents,  also  for  three- 
phase  alternating  current  power  circuits.  This  type  of  circuit 
breaker  is  made  of  a  capacity  from  five  to  two  hundred  amperes, 
for  use  on  circuits  of  two  hundred  and  fifty  volts  or  under. 


I  T-H  CIRCUIT  HKEAKKR 
FOR  USE  ON  CARS 


83 


PLATE  O 

I-T-E  CIRCUIT  BREAKER 
STANDARD  SWITCHBOARD  TYPE.     TRIPLE  POLE. 


LIGHTNING  ARRESTERS 


IGHTNING  arresters,  in  their  function,  bear 
the  same  relation  to  the  potential  stress  of  the 
station  as  the  circuit  breaker  bears  to  the  cur- 
rent demand,  and  their  purpose  is  to  offer  to  a 
high  potential  discharge  a  path  to  ground  where 
it  can  pass  off,  rather  than  enter  the  station  or 
the  protected  consumption  devices,  and  break 
down  their  insulation  in  the  effort  of  this  dis- 
charge reaching  the  earth. 

Lightning  discharges  have  peculiar  characteristics  which  make 
it  comparatively  easy  to  divert  them.  A  discharge  of  lightning  is 
supposed  to  be  a  rush  of  high  potential  which  possesses  an  enor- 
mous frequency,  and  consequently  inductive  circuits  arrest  its  flow; 
in  this  way  discharges  can  be  damped  back  from  entering  the 
station,  and  there  will  be  an  accumulation  of  potential  adjacent  to 
the  inductive  portion  of  this  circuit.  If  an  air  gap  be  connected 
here,  and  one  side  connected  to  the  charged  line,  and  the  other  side 
of  the  gap  connected  to  the  ground,  the  discharge  will  jump  this 
gap  and  pass  to  ground  and  be  equalized,  rather  than  force  its  way 
through  the  throttling  inductive  circuit.  In  order  to  accomplish 
this  result,  the  conductor  is  wound  into  a  number  of  convolutions, 
not  over  twenty,  on  a  four-inch  diameter  mandrel,  and  these  turns 
are  interposed  between  the  lightning  arrester  and  the  apparatus  to 
be  protected,  preferably  very  near  the  lightning  arrester  itself. 
This  protects  the  station  from  the  discharge ;  but  when  the  dis- 

85 


LIGHTNING   ARRESTERS 

charge  passes  the  air  gap,  it  so  reduces  the  resistance  of  this  gap, 
that  when  an  active  circuit  is  thus  protected,  the  main  current 
follows  to  ground  and  maintains  an  arc  over  the  gap.  For  the  pur- 
pose of  again  rupturing  this  circuit,  several  devices  are  used. 

THE  THOMSON-HOUSTON    LIGHTNING  ARRESTER 

Fig.  78  shows  type  of  magnetic  lightning  arrester.  Under  nor- 
mal conditions  the  current  from  the  generator  passes  through  the 
electro-magnetic  windings  to  the  right  hand  wing  of  the  arrester, 
and  then  to  line,  the  left  hand  wing  being  connected  to  earth.  The 
result  of  the  current  flowing  through  this  electro-magnet  produces 

a  strong  magnetic  effect  at  the  ends  of  the  mag- 
net, which  is  projected  across  the  air  gap ;  this 
forces  the  arc  away  along  the  curving  wing 
edges,  until  it  becomes  too  attenuated  to  be 
maintained  by  the  machine  potential.  Practi- 
cally this  occurs  instantly,  and  the  arrester  is 
then  ready  for  another  lightning  stroke.  Each 
arrester  protects  its  own  side  of  the  line,  and 
FlG  78  therefore  two  are  required  for  each  circuit.  The 

illustration  shows  the  form  of  arrester  usually  used  on  switchboards 
for  central  station  protection. 

WESTINGHOUSE  TANK   ARRESTER 

The  action  of  this  arrester  is  to  maintain  an  artificial  ground  of 
fairly  high  resistance  on  the  lines  to  be  protected,  only  when  they 
are  hazarded,  and  this  type  of  leak  arrester  has  been  developed  in 
order  that  there  be  no  actual  severance  of  the  ground  connection 
from  the  circuit  to  be  protected ;  for  in  an  arrester  possessing  an  air 

86 


WESTINGHOUSK   TANK  ARRESTER 


+  BU53 


gap,  an  abnormal  potential  must  exist  before  the  device  operates. 
Here  the  systems  to  be  protected  are  connected  to  a  leak  to  ground 
during  times  of  danger,  and  has  electrically  the  effect  of  bringing 
the  line  to  the  level  of  the  earth ;  for  through  this  leak  both  line 

and  earth  are  main- 
tained at  the  same 
potential,  and  dis- 
charges pass  off  to 
ground  through  this 
leak.  An  inductive 
circuit  is  usually 
interposed  between 
the  apparatus  to  be 
protected  and  the 
external  line  and 
leak,  in  order  to 
force  this  discharge 
FIG.  79  to  ground. 

A    leak    arrester 

allows  the  surging  of  induced  potential  in  the  line  protected,  due 
to  the  inductive  effects  of  charged  clouds  over  the  line  to  follow 
the  same  potential  values  as  the  earth  over  which  they  are  strung. 
The  type  of  leak  arrester  is  only  suitable  to  protect  circuits  where 
one  side  of  the  circuit  only  is  to  be  protected.  Fig.  79  shows  this 
type  of  arrester,  and  the  tank  leak  is  plugged  when  the  system  is 
threatened.  There  are  generally  three  tanks  employed,  having 
between  them  inductive  circuits,  "A,"  "  B,"  and  "  C,"  so  that 
if  the  discharge  passes  one,  it  is  restrained  still  further  by  the 
other  two. 


WESTINGHOUSE  TANK   ARRESTER 

There  are  a  great  number  of  types  of  arresters  using  fuses  with 
air  gaps,  the  fuse  being  severed  by  the  current  following  the 
discharge ;  but  as  discharges  follow  each  other  rapidly,  continuous 
protection  is  desirable. 

There  are  also  condenser  arresters  in  which  the  lightning  dis- 
charge passes  from  one  plate  to  the  other ;  but  these  plates  being 
in  series,  the  initial  potential  of  the  circuit  cannot  maintain  a  dis- 
continuous arc. 


THE   NON-ARCING   LIGHTNING   ARRESTER 

It  has  been  discovered  that  with  certain  metals,  when  they  form 
the  surfaces  for  a  spark  gap,  an  alternating  current  will  not  main- 
tain an  arc  between  these  surfaces,  due  to  the 
cooling  effect  of  the  terminals  and  the  character 
of  the  vapor  of  the  metal  in 
the  arc.  Fig.  80  shows  the 
type  of  the  Westinghouse 
Non-Arcing  Arrester,  which 
is  constructed  embodying 
this  principle,  and  which 


FIG.  80 


consists  of  a  number  of  cylinders  of  non-arc- 
ing metal,  forming  several  gaps  between  them, 
which  are  jumped  by  the  high  potential  dis- 
charge ;  the  alternating  current  does  not  follow 
and  maintain  an  arc  across  these  spaces  or 
gaps,  and  this  form  of  device  is  largely  used 
in  alternating  current  switchboards,  where  it 
is  considered  policy  to  place  the  arrester  on  the  switchboard 
itself. 


FIG.  Si 


88 


THE   NON-ARCING   LIGHTNING   ARRESTER 

Yet  another  form  of  arrester  is  shown.  In  Fig.  81,  in  this  case, 
the  current,  in  its  passage  to  the  ground  after  following  the  dis- 
charge through  the  gaps,  actuates  an  electro-magnet  which  pulls 
an  arm,  and  lengthens  the  air  gap  until  the  arc  is  extinguished. 


I860 


89 


THE  LOW  TENSION  SWITCHBOARD 


F  the  elements  of  design,  common  to  both  the 
isolated  plant  and  the  large  low  tension  cen- 
tral station  switchboard,  both  can  be  treated 
together.  Taking  the  simpler  forms  first,  and 
afterwards  considering  the  special  conditions 
necessary  to  be  met  by  the  switchboard,  when 
used  to  control  the  more  intricate  methods  of 
central  station  operation  and  distribution- 
methods  recently  introduced  to  give  the  proper 
potential  supply  over  the  expanding  areas  of  the  external  network 
of  conductors,  and  also  for  working  of  the  storage  battery  in 
connection  with  the  generators  of  the  station. 

The  isolated  plant  usually  consists  of  several  generators  and  a 
number  of  feeders  to  centres  of  distribution.  The  actual  assembly 
of  the  apparatus  on  the  switchboard,  and  its  relative  position,  is  so 
largely  determined  by  the  local  conditions  to  be  met,  and  the  con- 
venience in  handling,  that  to  illustrate  the  different  methods  of 
assembly  would  not  be  of  much  value,  but  the  method  of  connect- 
ing the  different  appliances  is  common  to  all  the  systems. 

Diagram  i  gives  the  connections  where  a  shunt  dynamo  is  oper- 
ated on  a  simple  two-wire  system.  In  this  case  the  two  terminals 
of  the  dynamo  are  brought  to  the  switchboard  through  the  dynamo 
leads  to  a  double-pole  switch. 

The  connections  are  usually  made  to  the  switch,  so  that  the 
dynamo  feeds  through  the  fuses  and  then  through  the  switch 


90 


THE  LOW  TENSION  SWITCHBOARD 

mechanism  to  the  bus  bar,  so  that  if  the  switch  is  pulled,  it  can  be 
fused  when  there  is  no  current  on  the  switch.  Circuit  breakers 
are  usually  inserted  in  the  dynamo  lead  before  it  is  tapped  on  the 
dynamo  switch ;  the  main  current  is  here  taken,  one  leg  to  the  bus 

bar,  and  the  other  leg  to  the 
shunt  dynamo  amperemeter 
"A,"  and  then  to  the  other 
bus  bar.  The  dynamo  regula- 
tor "R"  is  connected  in  series 
with  the  shunt  field,  the  field 
wire  being  brought  from  the 
dynamo  for  this  purpose;  one 
end  of  the  field  being  connected 
to  one  lead  at  the  dynamo,  and 
the  other  end  connected  to  the 
other  dynamo  lead  at  the  switch- 
board. The  voltmeter  "V"  is 
connected  across  the  bus  bars, 
and  the  ground  detector 
"GTL,"  in  one-hundred-and- 
F  d  S  H  ten-volt  system,  consists  of  two 
lamps  in  series  across  the  bus 
Diagram  No.  1.  bar>  a  middle  connection  being 

taken  between  the  two  lamps  to 
ground.  Generally  the  ground 
connection  is  provided  with  a  plug  "  P,"  so  that  the  system  is  only 
grounded  when  the  test  is  being  made. 

In  connecting  two  or  more  dynamos  that  are  to  be  worked  in 
multiple,  provision  has  to  be  made  so  that  these  dynamos  can  be 


THE  LOW  TENSION  SWITCHBOARD 

thrown  together  without  any  fluctuation  to  the  potential  of  the 
system. 

Diagram  2,  Fig.  i,  shows  a  method  where  a  dynamo  galvano- 
meter is  used  for  this  purpose,  and  is  so  connected  that  the  dynamo 
feeds  into  the  bus  bar  one  side  direct,  and  the  other  side  through 
the  dynamo  galvanometer,  which  usually  bridges  the  open  dynamo 
switch,  two  single  pole  switches  being  used  when  this  method  is 
employed  for  throwing  in  dynamos. 

It  is  evident  that  when  no  current  flows,  the  potential  on  the 
dynamo  and  the  bus  bar  must  be  the  same,  when  the  dynamo  can 
be  thrown  on  the  system.  Fig.  2  shows  another  zero  method 
where  the  potential  for  the  generator  and  the  potential  on  the 
buses  both  act  on  the  same  magnetic  system  differentially;  when 
the  currents  through  them  both  are  equal,  the  needle  of  the  differ- 
ential galvanometer  "  D  G '  will  point  to  zero,  and  the  dynamo  is 
ready  to  be  thrown  in. 

Both  of  these  zero  methods  possess  the  inherent  objection  that 
they  give  the  same  indication  when  there  is  no  current  flowing 
through  the  instrument  as  when  they  are  ready  to  be  thrown  in, 
and  mistakes  have  arisen  from  this  cause,  and  have  led  to  volt- 
meters being  used  for  this  purpose.  Each  generator  is  supplied 
with  a  pair  of  contact  buttons  of  a  voltmeter  switch  "V  S," 
which  are  connected  direct  to  the  two  leads  of  the  dynamo,  and 
the  voltmeter  can  be  connected  directly  to  any  machine  and  its 
potential  raised  until  it  is  the  same  as  the  bus,  when  it  can  be 
thrown  in. 

In  compound  generators,  where  more  latitude  can  be  allowed  in 
the  potentials  of  the  generators  being  thrown  in,  pilot  lamps  "PL" 
may  be  sufficient  to  give  the  proper  indication  when  they  are  con- 

92 


No£. 


sl   s. 


D. 


'l 


PL 


D 


TT 


G    L 


D. 


o     o          o 
I 


F.o3. 


/ww 

DG. 


?v.s. 


PL 


D 


THE   LOW   TENSION   SWITCHBOARD 

nected  across  the  dynamo  leads.  These  two  last  connections  are 
shown  in  Diagram  2,  Fig.  3. 

The  above  connections  show  those  used  for  shunt  generators, 
where  the  rheostat  is  the  only  method  of  regulation ;  but  isolated 
plants  are  usually  provided  with  compound  wound  machines,  and 
provision  has  to  be  made  on  the  switchboard  for  equalizing  connec- 
tions, as  it  is  the  usual  practice  in  isolated  plants  to  have  the  equal- 
izing bus  on  the  switchboard. 

The  proper  connection  of  the  equalizer  plays  an  important  part 
in  compound  dynamo  regulation,  and  the  resistance  of  the  leads 
from  the  dynamos  to  the  switchboard,  both  equalizing  and  series 
leads,  should  be  calculated  as  follows : 

In  all  generators  of  the  same  size  and  having  the  same  com- 
pounding characteristics,  the  resistance  from  the  equalizing  bus  to 
the  bus  connected  to  the  series  side  would  be  equal  for  all  genera- 
tors. Where  these  generators  are  different  sizes,  the  drop  of 
potential  on  the  equalizer  and  series  leads  should  be  the  same  for 
all  compound  generators,  when  these  generators  are  working 
together  and  carrying  their  full  load.  Where  the  dynamos  are  not 
of  the  same  type  nor  the  same  compounding  characteristics,  the 
resistance  of  the  equalizing  circuit  will  have  to  be  such  that  the 
drop  from  all  generators  will  be  the  same  when  they  take  their 
maximum  load  together;  but  it  is  hardly  possible  to  compound 
dynamos  of  very  different  characteristics  together,  so  that  they  will 
pick  up  their  proportional  load  equally  among  themselves,  and 
only  the  best  approximate  condition  can  be  obtained,  when  they 
will  take  their  full  load  together. 

If  it  is  necessary  to  operate  compound  generators  on  two  or 
more  potentials,  each  potential  must  have  its  independent  equalizing 

94 


THE  LOW  TENSION  SWITCHBOARD 

bus,  so  that  the  equalizing  leads  can  be  shifted  to  the  equalizing  bus 
to  correspond  with  the  potential  bus,  on  which  that  dynamo  is  to  be 
operated,  in  order  that  the  proper  regulation  can  be  effected  by  the 
series  field.  Diagram  3  gives  the  connections  for  two  compound 
generators  connec- 

L     <fl»GTL( 


ted  in  multiple. 
This  diagram  shows 
a  three-pole  switch 
used  for  this  pur- 
pose. The  third  or 
middle  clip  should 
be  made  longer,  so 
that  the  equalizing 
connection  can  be 
established  before 
the  generator  is 
thrown  in  on  the 
system.  An  equal- 
izing bus  is  provided 
in  this  diagram, 
which  is  the  usual 
practice,  where 
there  are  a  number 
of  machines  work- 
ing together. 

Another  method,  which  is  sometimes  used,  is  to  connect  the 
equalizer  and  also  the  dynamo  lead  from  the  equalizer  side  of  the 
generator  to  a  double  pole  switch.  This  can  be  thrown  in  and  the 
dynamo  brought  up  to  potential,  and  a  single  pole  switch  can  be 


TTeecb?v  5wi+cl\e3. 

No3. 


95 


THE  LOW  TENSION  SWITCHBOARD 

closed  on  the  open  side  of  the  generator  to  throw  the  machine  in 
on  the  system.  This  method  of  connection  has  its  advantage : — if 
there  is  much  distribution  drop,  and  if  the  generators  are  over- 
compounded  to  take  care  of  it,  and  a  number  of  machines  work 
together  in  multiple  to  supply  the  full  load  when  this  maximum 
drop  occurs,  it  is  evident  that  when  one  machine  is  operated  to 
supply  the  minimum  load,  the  generator  will  normally  give  too 
high  a  potential,  and  hand  regulation  will  be  necessary  in  order  to 
obtain  the  proper  potential ;  whereas,  if  the  series  and  compound 
connection  were  left  in  circuit  of  the  idle  machines,  they  would 
reduce  the  normal  over-compounding  of  the  active  machine  as  the 
load  on  the  plant  decreased.  In  this  way  better  regulation  can  be 
produced  and  the  over-compounding  of  the  machine  is  somewhat 
controlled.  This  also  avoids  ever  putting  in  a  compound  machine 
in  circuit  without  first  equalizing. 

Another  method  is  to  have  the  voltmeter  by  which  the  genera- 
tors are  brought  up  to  potential,  not  connected  across  the  machine 
until  the  equalizer  switch  is  thrown,  and  in  this  way  avoid  putting 
in  the  generator  without  first  equalizing. 

The  circuit  breaker  should  always  be  connected  in  the  lead  on 
the  opposite  side  of  the  dynamo  from  the  series  winding,  for  it 
would  require  a  double  pole  circuit  breaker  to  open  the  circuit  on 
the  compounding  side  of  the  machine.  Diagram  4  shows  the  con- 
nection for  a  three-wire  two-dynamo  system,  which,  in  effect,  is  two 
dynamos  in  series,  the  positive  of  one  brush  being  connected  to  the 
negative  of  the  next,  which  forms  the  neutral  connection.  Besides 
the  apparatus  required  on  the  two-wire  switchboard,  the  three-wire 
system  requires  two  voltmeters,  one  on  each  side  of  the  system,  and 
the  three-wire  ground  detector  should  have  two  lamps  in  series 

96 


THE  LOW  TENSION  SWITCHBOARD 


between  the  positive  and  negative  bus  to  ground,  and  one  lamp 
between  neutral  bus  to  ground;  the  ground  detector  should  be 
provided  with  a  double  throw  switch,  so  that  the  positive  or  nega- 


GTL 


TOT 


D 


tive  side  of  the  system  can  be  tested  with  the  same  detector,  three- 
pole  switches  being  used  for  all  feeders. 

Sometimes  the  neutral  connections  are  made  between  the 
dynamos  themselves,  and  the  neutral  bus  is  only  used  behind 
the  feeder  board  and  connected  to  the  common  dynamo  neutral  in 


97 


THE  LOW  TENSION  SWITCHBOARD 

the  dynamo  room.  This  saves  nearly  one-third  of  the  copper  in 
leads  over  that  required  to  bring  every  terminal  of  the  dynamo  to 
the  switchboard. 

Where  dynamos  are  to  be  used  on  either  side  of  the  system,  they 
have  to  be  provided  with  a  double  throw  switch,  so  that  the)' 
can  be  connected  on  either  side,  and  the  connections  must  be 
made  so  that  the  polarities  will  be  right  for  either  position  of  the 
switch. 

Diagram  5  shows  the  connection  for  two  sets  of  compound 
dynamos  connected  to  a  three-wire  system.  Here  the  only  depart- 
ure from  Diagram  4  is  that  an  equalizer  has  been  added,  one  for 
each  side  of  the  system,  and  of  course  if  these  machines  are  to  be 
used  on  either  side  of  the  system,  a  double  throw  three-pole  switch 
would  be  required,  so  that  the  dynamos  on  one  side  of  the  system 
always  equalize  on  the  same  bus. 

There  are  a  number  of  methods  used  where,  from  a  single 
dynamo  of  two  hundred  and  twenty  volts,  a  three-wire  system  is 
operated.  These  systems  require  an  auxiliary  device  which  would 
equalize  the  loads  between  the  two  sides  of  the  system.  It  is  evi- 
dent that  if  two  dynamos  were  connected  together  in  series  across  a 
22o-volt  two-wire  system,  and  the  neutral  taken  from  the  common 
connection  of  these  two  dynamos,  and  if  an  unbalanced  load  were 
operated,  the  dynamo  on  the  highly  loaded  side  of  the  system  would 
tend  to  operate  as  a  dynamo  and  pump  current  into  that  side  of  the 
system,  and  balance  the  system  external  to  the  generator  itself. 
The  switchboard  for  this  system,  as  far  as  the  generators  go,  is  sim- 
ply a  two-wire  switchboard,  but  the  equalizer  or  compensator  is  con- 
nected across  from  the  positive  to  the  negative,  and  the  neutral  taken 
from  the  common  junction  of  these  two  to  the  feeder  switches  only. 

98 


-HIU 


Q 


-HU 


THE  LOW  TENSION  SWITCHBOARD 


Diagram    No    B   A . 


A  storage  battery  has  also  been  proposed  for  affecting  an  equal- 
ization of  the  load  between  the  two  sides  of  the  three-wire  system, 
but  the  connections  in  this 
case  are  the  same  as  an 
equalizer.  A  five-wire  sys- 
tem is  usually  connected  as  a 
three-wire  system,  except  in 
having  four  dynamos  in  series  with  connection  between  each  gen- 
erator, and  the  dynamos  connected  between  the  different  buses  at 
the  back  of  the  board.  The  connections  for  the  above  methods  are 

shown  in  Diagram  6A. 

It  is  often  important, 
in  isolated  plant  work, 
that  the  motors,  espe- 
cially if  elevator  motors  be 
used  during  light  loads, 
be  operated  on  indepen- 
dent generators;  these 
loads  fluctuate  violently 
and  the  generators  can- 
not regulate  quickly 
enough  in  order  that  the 
constant  potential  be  kept 
on  the  lighting  system. 

The     switchboard      is 
separated  up  into  two  bus 
systems — lighting    and 
power — and  each  genera- 
te 82  tor    is    provided    with    a 


100 


THE  LOW  TENSION  SWITCHBOARD 

double  throw  switch,  operating  on  power  in  one  position  and  light- 
ing in  another. 

In  large  apartment  houses,  public  buildings  and  asylums,  it  is 
also  advisable  to  separate  the  public  lighting  from  the  private  light- 
ing, and  supply  it  by  the  same  or  different  generators.  This  is 
taken  care  of  by  providing  the  generators  with  double  throw 
switches,  and  also  supplying  the  feeders  with  double  throw  switches, 
if  they  are  to  be  fed  from  different  sources  of  supply. 

Some  methods  of  making  back  connections  for  isolated  plant 
switchboards  are  shown  in  Fig.  82. 


101 


LOW  TENSION  CENTRAL  STATION  SWITCHBOARDS 

EFINITE  control  of  potential  over  a  large  net- 
work of  low  tension  conductors  has  required 
a  variety  of  methods  in  the  handling  of  these 
feeders  at  the  switchboard,  in  order  to  pro- 
duce this  variation  of  potential  economically. 
The  first  means  resorted  to  in  order  to 
create  this  difference  of  potential  on  the 
feeder  terminals  was  to  insert  an  adjustable 
resistance  to  compensate  for  the  unequal  losses  occurring  in  the 
feeders,  so  that  the  current  would  be  delivered  to  the  mains  at  a 
uniform  potential  throughout  the  system.  This  method,  however, 
is  uneconomical,  both  as  regard  the  amount  of  energy  consumed 
for  the  purpose  of  regulation  and  the  valuable  space  occupied  by 
this  method. 

Fig.  B,  of  the  introductory,  shows  this  method  with  equalizers, 
as  installed  in  the  old  Adams  Street  Station  of  the  Chicago  Edison 
Company.  This  method  has  now  become  practically  obsolete ;  but 
as  the  low  potential  systems  have  been  expanding  over  large  areas 
to  include  a  greater  number  of  customers,  it  has  again  become 
necessary  to  deliver  current  at  the  station  ends  of  these  feeders  at 
different  potentials,  to  compensate  for  the  unequal  loading  of  the 
system.  This  is  affected  under  some  conditions  by  running  the 
dynamos  at  different  potentials,  which  supply  independent  busses, 
the  feeders  being  so  arranged  that  they  can  be  thrown  on  any  of 
these  busses  and  supplied  with  current  at  the  proper  potential  to 


102 


LOW  TENSION  CENTRAL  STATION  SWITCHBOARDS 

make  good  the  feeder  losses  and  deliver  their  current  to  the  mains 
at  a  uniform  potential. 

When  the  units  in  the  station  are  small,  they  can  be  divided  up 
on  the  different  busses  with  comparatively  high  economy ;  but  as 
the  central  station  business  has  increased,  and  the  plants  have 
adopted  large  units,  both  on  the  score  of  economy  for  the  first  cost 
and  operation  and  to  increase  the  kilowatt  output  to  the  square 
foot  of  floor  space,  these  practical  conditions  have  greatly  altered 
modern  central  station  switchboard  design.  The  condition  of  oper- 
ating the  units  at  an  economical  load  must  be  maintained,  while 
the  feeder  service  requires  several  potentials  to  be  delivered  to  it. 

The  booster  system  has  been  devised  in  order  to  change  the 
potential  of  the  current  delivered  by  the  generators  UD  D"  in 
Diagram  6.  In  order  to  clearly  understand  the  connections  for  the 
system,  the  following  explanation  is  made  regarding  its  action  in 
the  case  of  the  three-potential  system: 

In  this  case,  the  medium  potential  bus  is  fed  directly  by  the 
units  operating  the  station,  and  the  current  is  delivered  from  the 
medium  bus  to  the  high  potential  bus,  through  the  armature  of  a 
dynamo  whose  field  is  separately  excited,  the  current  capacity  of 
the  armature  being  sufficient  to  carry  the  loads,  at  which  it  would 
be  uneconomical  for  one  of  the  units  to  operate.  The  current,  in 
passing  through  this  armature,  has  its  initial  potential  raised,  and 
the  amount  of  this  increased  potential  is  controlled  by  a  field  regu- 
lator "R,"  in  series  with  the  dynamos'  separately  excited  field;  the 
currents  which  supply  the  bus  of  lower  potential  than  the  medium 
bus  also  flow  through  an  armature,  but  in  this  case  the  initial 
potential  of  the  current  is  reduced  before  it  is  delivered  to  the 
low  potential  bus.  This  dynamo  is  operating  as  a  motor,  and 


10; 


LOW  TENSION  CENTRAL  STATION  SWITCHBOARDS 

the  potential  of  the  current  passing  through  it  can  be  regulated 
by  means  of  a  field  rheostat.  Shunt  wound  boosters  are  usually 
used  in  low  potential  work  which  is  controlled  by  the  shunt 
field  only. 

In  the  three-wire  system  two  boosters  are  required  for  each 
potential,  and  it  is  the  usual  practice  to  couple  these  boosters 
together,  forming  one  continuous  line  of  shafting,  to  which  is  also 
coupled  a  motor  for  the  purpose  of  keeping  the  boosters  up  to  full 
speed,  and  making  good  the  losses  due  to  transformation  and  the 
unequal  loading  of  the  high  and  low  busses. 

Diagram  6  shows  the  method  employed  for  connecting  boosters 
to  a  three-wire  system. 

It  is  evident  that  if  one  dynamo  could  be  arranged  to  give 
several  potentials,  the  efficiency  of  output  would  be  raised  and 
the  losses  inherent  in  the  operation  of  the  boosters  would  be  saved. 
There  have  been  several  methods  proposed  for  this  purpose,  but 
when  a  series  wound  armature  rotates  in  a  multipolar  field,  and  a 
load  falls  on  one  circuit  supplied  by  a  section  of  this  armature,  a 
redistribution  of  magnetism  will  occur,  caused  by  the  unequal  load- 
ing of  this  symmetrical  armature ;  this  will  give  an  unequal  poten- 
tial delivery  to  the  circuits  from  this  armature,  and  a  variation  of 
potential  beyond  the  control  of  the  regulator.  If  this  condition  is 
avoided  in  the  design  of  the  machine,  it  becomes  both  expensive  in 
first  cost  and  uneconomical  in  operation ;  but  with  a  symmetrical 
external  distribution  system,  with  regard  to  the  station  and  feeders 
which  are  tapped  radially  into  a  concentric  main,  and  if  a  load  falls 
on  one  part  of  this  main,  and  that  section  of  the  multipolar  gen- 
erator has  its  field  increased,  the  distribution  of  magnetism  in  the 
concentric  field  will  be  identical  with  that  of  the  distribution  of 


LOW  TENSION  CENTRAL  STATION  SWITCHBOARDS 

current  in  the  concentric  main ;  in  this  way  a  compounding  effect 
can  be  obtained  external  to  the  dynamo  itself. 

In  certain  cases,  economy  may  be  shown  by  inserting  regulating 
resistances  between  the  high  bus,  and  busses  of  lower  potentials  may 
this  way  be  obtained  where  the  current  demands  on  the  busses  of 
lower  potential  are  small,  and  the  losses  in  these  resistances  are 
less  than  that  caused  by  a  partly  loaded  engine  and  generator 
working,  on  this  reduced  potential.  This  method  also  allows  keep- 
ing the  generator  efficiency  high  by  working  all  the  units  under 
the  maximum  possible  loads  for  the  different  daily  variable  outputs 
of  the  station;  this  result  can  be  obtained  by  the  proper  switch- 
board design,  which  will  also  effect  a  large  operating  economy. 

In  other  methods  of  producing  the  several  potentials  required 
for  close  regulation  on  the  external  distribution  system,  the  storage 
battery  is  one  which  is  coming  into  use,  and  here  the  different 
busses  obtain  their  potentials  from  different  cells  of  the  same  series 
of  storage  batteries,  and  the  potentials  on  these  busses  can  be  regu- 
lated by  the  battery-regulating  switches.  This  gives  the  only 
method  by  which  the  regulation  potential  on  the  feeders  can  be 
affected  without  changing  the  loading  on  the  generator. 

As  the  feeder  has  to  be  supplied  with  several  potentials,  switch- 
ing arrangements  have  to  be  provided  so  that  these  feeders  can  be 
connected  at  will  to  the  various  potential  busses  supplied  by  the 
generating  apparatus.  Where  only  two  potentials  are  required,  a 
.double  throw  switch  is  used  and  the  feeder  is  brought  to  the  centre 
clip,  when  connection  is  made  to  either  potential. 

Where  three  potentials  are  used,  double  pole  switches  can  also 
be  used  by  grouping  the  nearby  or  low  resistance  feeders,  so  that 
they  can  be  connected  to  common  bus  and  low  bus,  and  the  outline 

1 06 


LOW  TENSION   CENTRAL   STATION   SWITCHBOARDS 

or  high  resistance  feeders,  by  means  of  a  double  throw  switch,  can 
be  connected  to  common  and  high  bus;  the  dynamos  would,  of 
course,  have  to  have  three-way  switches  in  this  case,  so  that  they 
could  be  operated  on  any  bus,  as  required. 

Where  the  distribution  system  requires  considerable  variation  in 
potential,  a  double  throw  switch  could  be  used  for  a  considerable 
number  of  potentials  for  the  different  feeders,  if  they  are  properly 
grouped,  and  if  the  drop  is  so  slight  at  light  loads  that  all  feeders 
can  be  supplied  from  the  common  bus.  Under  these  conditions  all 
the  busses  can  be  tied  together  by  tie  switches,  or  all  feeders  can 
be  thrown  on  one  bus.  WThere  the  feeders 
themselves  have  to  be  supplied  with  more 
than  two  potentials  during  the  load  fluctua- 
tions on  the  station,  several  forms  of  switches 
have  been  devised  for  this  purpose.  The 
simplest  form  is  a  double  pole  double  throw 
switch,  having  each  blade  on  an  indepen- 
dent handle ;  in  this  way  a  feeder  can  be  supplied  from  any  of  four 
potentials,  and  also  two  busses  can  be  connected  together  by  this 
switch  at  low  loads.  See  Fig.  83.  The  radial  form  of  switch  for 

the  same  purpose  has  different  bus  bars  con- 
nected to  clips  and  disposed  concentrically 
around  the  centre ;  the  switch  plate  is  pivoted 
so  that  it  can  be  thrown  in  on  any  of  these 
busses  when  swung  around  in  position.  For 
this  construction,  see  Fig.  84. 

Another  form  has  been  developed  for  this 
purpose,  where  the  switch  blade  is  detachable,  and  can  be  engaged 
with  several  terminals  which  align  with  the  different  bus  terminals 


83 


107 


LOW  TENSION  CENTRAL  STATION  SWITCHBOARDS  • 

and  the  movable  blade  inserted ;  in  this  way  the  feeder  can  be  con- 
nected to  any  bus.     See  Fig.  85. 

In  central  station  switchboards,  there  are  several  general 
methods  of  distributing  the  controlling  and  regulating  of  apparatus. 
One  way  is  to  concentrate  all  the  regulators  and  field  switches  at 
one  point,  and  the  dynamo  switches,  am- 
meters and  galvanometers  on  the  dynamo 
switchboards. 

The  most  prevailing  method  is  to 
assemble  the  regulator,  field  switch, 
dynamo  galvanometer,  dynamo  switch 
and  amperemeter  on  the  dynamo  board, 


all  mounted  on  the  same  panel.  The  voltmeters  are  placed  in 
some  conspicuous  position  with  the  pressure  switches;  by  using 
edgewise  instruments,  a  density  of  four  hundred  kilowatts  per  run- 
ning foot  was  obtained  in  the  switchboard  designed  for  The  Chicago 
Edison  Company  by  the  author.  The  character  of  bus  bar  connec- 
tions required  for  the  carrying  of  one  hundred  and  eighty  thousand 
amperes  from  the  lower  dynamo  board  to  the  upper  three-potential 
feeder  board,  which  was  located  above  the  dynamo  board  in  the 
Chicago  Edison  Company's  station,  is  shown  in  Fig.  87. 

The  matter  of  field  connections  has  to  be  carefully  considered, 
for  with  large  low  potential  units,  a  high  induced  potential  is 
created  when  the  field  circuit  is  broken ;  this  will  tend  to  break 
down  the  insulation,  and  is  the  only  way  in  which  a  hazardous 
potential  can  be  produced  in  a  low  potential  system. 

The  method  of  connecting  the  field  in  any  generator  will 
depend  upon  the  system  which  is  supplied  by  that  unit.  The  self- 
exciting  method  is  when  the  field  is  connected  directly  across  the 

1 08 


tx 

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LOW  TENSION  CENTRAL  STATION  SWITCHBOARDS' 

terminals  of  the  generator ;  the  rheostat  is  included  in  this  circuit, 
and  when  the  armature  is  rotated  and  creates  a  potential,  due  to  the 
residual  magnetism  in  the  field,  it  sends  a  current  circulating 
through  the  field  windings,  and  in  this  way  builds  up  the  genera- 
tor's potential.  The  bus  exciting  method  is  where  the  field  is  con- 
nected to  the  bus  bars  and  excited  by  a  potential  external  to  its 
own.  This  method  has  the  advantage  of  bringing  the  machine 
quickly  up  to  the  proper  potential,  and  always  of  the  right  polarity; 
but  when  the  field  is  to  be  withdrawn  from  the  bus  bar,  after  the 
machine  is  shut  down,  the  field  must  first  be  short-circuited  through 
a  non-inductive  resistance,  such  as  a  lamp  bank,  before  it  is  broken, 
in  order  to  reduce  the  potential  of  discharge. 

The  advantage  of  the  self-exciting  method  is  in  the  feature  that, 
when  the  dynamo  is  shut  down,  the  field  dies  away  with  the  fall  of 
potential  on  the  generator ;  but  in  large  multipolar  units,  the  poten- 
tial may  rise  very  slowly,  and  for  this  reason  bus  exciting  is 
largely  used. 

Separately  exciting  methods  have  no  difference  in  their  connec- 
tion from  the  bus  exciting,  except  a  separate  generator  is  used  for 
field  exciting.  A  condition  arises  where  it  is  very  advisable  to 
have  the  field  exciting  of  the  generators  so  arranged  that  any  of 
the  generators  of  the  station  can  be  used  temporarily  as  a  sepa- 
rate exciter,  when  there  occurs  a  very  severe  load  or  a  short-circuit 
on  the  external  distribution  system.  It  is  necessary  to  provide  this 
method  in  order  to  hold  up  the  potential  of  the  generators  working 
on  a  short-circuit,  as  the  reaction  of  the  armature  under  these  con- 
ditions is  so  great  that  it  kills  the  field,  and  the  generator  loses  its 
potential  when  the  field  is  excited,  and  the  distribution  is  supplied 
from  the  same  bus  bar,  and  the  station  falls  flat.  Diagram  7  shows 


no 


LOW  TENSION  CENTRAL  STATION  SWITCHBOARDS 


how  by  using  a  special  field  switch,  all  the  fields  can  be  excited 
from  any  generator.  This  method  is  only  advised  to  be  used  in  the 
case  of  emergency  or  short-circuit,  and  the  proper  connections  can 

be  quickly  made  before  the 
potentials  have  fallen,  by  in- 
serting a  dynamo  on  the  field 
bus  and  withdrawing  the 
switch  that  connects  the  field 
and  main  busses  together. 

Another  method,  known 
as  the  Donshea  method, 
combines  the  good  features 
of  both  the  bus  exciting  and 
separately  exciting  methods.  For  connections  see  Diagram  8. 
The  field  switch  "A"  interlocks  with  one  leg  to  the  dynamo 
switch;  to  the  other  leg  the  field  is  permanently  connected.  If 
dynamo  switch  "B"  and  field  switch  "A"  are 
thrown,  the  field  of  dynamo  "B"  is  excited  by  the 
pressure  on  the  busses.  The  dynamo  is  thrown  on 
the  system  by  closing  dynamo  switch  "  C."  This 
switch  is  so  arranged  that  when  the  main  blade  is 
withdrawn,  it  carries  with  it  field  switch  "  A," 
which  is  also  electrically  connected  to  it.  When 
these  interlocking  switches  are  withdrawn,  the  field 
circuit  is  from  the  terminal  of  the  dynamo,  through 
field  resistance  box,  field  switch  and  dynamo  switch 
blade,  then  back  to  the  other  brush  of  the  dynamo.  In  this  posi- 
tion of  switches  the  dynamo  is  self-excited  and  the  field  will  die 
away  with  the  voltage  on  the  armature. 


III 


LOW  TENSION  CENTRAL  STATION  SWITCHBOARDS 

The  Potter  method,  Diagram  9,  is  applicable  to  compound 
generators,  and  by  reason  of  the  field  being  also  excited  by  the 
series  winding  when  thrown  across  the  equalizer  and  positive  side 
of  the  system,  it  will  be  in  multiple  with  the  series  fields  of  the 
other  dynamos  in  operation,  and  the  cur- 
rent will  be  diverted  to  it,  exciting  the 
fields.  By  the  aid  of  this  initial  excitation, 
the  dynamo  can  be  brought  up  readily  to 
the  proper  potential  by  adjusting  the 
shunt  field,  and  when  its  proper  potential 
is  reached,  it  can  be  thrown  in  multiple 
with  other  generators. 


By  practising  this  method  of  exciting  dynamos,  compound 
machines  cannot  be  thrown  in  multiple  without  first  connecting  the 
series  field,  if  the  positive  pole  and  equalizer  be  connected  each 
to  one  leg,  by  double  pole  switches.  For  these  connections,  see 
Diagram  9. 


112 


RAILWAY  SWITCHBOARDS 

NOWING  the  extreme  conditions 
that  arise  in  railway  practice,  it 
is  required  of  the  electrical  en- 
gineer, in  designing  the  switch- 
board for  this  service,  to  fully 
protect  the  generating  apparatus 
from  the  shocks  due  to  sudden 
overloads,  and  an  automatic 
circuit  breaker  is  in  this  case 
a  necessity.  The  current 
passes  through  this  circuit  breaker,  then  through  the  ammeter 
shunt  or  the  ammeter  system  itself  to  the  negative  bus  bar. 

In  railway  practice,  the  positive  side  of  the  machine,  where  the 
trolley  is  positive,  is  connected  through  the  series  winding.  The 
equalizing  connection  is  taken  to  the  middle  point  of  the  switch  to 
the  equalizing  bus,  but  the  present  practice  in  power  stations  is  to 
equalize  at  the  dynamo,  and  the  equalizing  switch  either  mounted 
on  the  frame  of  the  dynamo  itself  or  on  a  pedestal  by  the  side  of 
the  dynamo.  In  other  cases  again,  the  equalizer  is  tied  together 
permanently  between  all  the  dynamos.  The  disadvantage  of  hav- 
ing the  equalizer  opened  is  that  there  is  a  danger  of  the  machine 
being  thrown  in  circuit  before  it  is  equalized.  In  order  to  provide 
against  this  accident,  several  suggestions  have  been  made;  one  is 
to  make  the  switch  at  the  dynamo  double  pole,  through  which  are 
carried  both  the  equalizer  and  positive  connections;  by  means  of 


RAILWAY   SWITCHBOARDS 

this  connection,  the  generator  cannot  be  thrown  in  from  the  gallery 

or  switchboard  without  having  the  equalizer  thrown  in  first. 

Another  method  has  been  proposed  where  the  throttle  of  the 

engine  is  connected  to  the  equalizer  switch,  so  that  when  it  is  open 

it  closes  the  equalizer 
switch ;  in  this  way  the 
generator  cannot  be 
thrown  in  before  it  is 
equalized. 

The  field  of  the 
railway  generator  may 
be  connected  up  in  two 
ways;  the  one  shown 
in  full  lines  is  the  bus- 
excited  method,  and 
the  one  shown  in  dot- 
ted lines  is  the  self- 
excited  method.  A 
dynamo  galvanometer 
or  voltmeter  is  ar- 
ranged across  the  dy- 
namo terminals  of  the 
dynamo  switch,  in 
order  to  show  when  the 
generator  is  of  the 

right  potential  to  be  connected  in  on  the  system.      Diagram   10 

shows  these  connections. 

It  is  also  usual  to  allow  for  a  panel  between  the  dynamo  and 

feeder  panels,  on  which  to  mount  the  main  ammeter,  integrating 


114 


R  A I  L\V  A  Y   S\YI  TC  H  BO  AR  DS 

wattmeter,  voltmeters  and  pressure  switches.  The  positive  is  only 
taken  to  the  feeder  board,  and  the  feeders  are  provided  with  a  single 
pole  switch,  ammeter,  circuit  breaker  and  reactance  coil  to  choke 
back  any  lightning  discharges  and  force  the  arrester  to  operate. 

The  dynamo  panels  should  be  provided  with  a  small  double  pole 
lighting  switch,  where  the  station  is  lighted  from  the  power  genera- 
tors, so  that  any  generator  can  light  the  station  independent  of  the 
power  bus.  This  lighting  circuit  should  be  looped  inside  of  the 
circuit  breakers. 

The  present  practice  indicates  that  the  best  results  obtained 
are  when  the  lightning  arresters  are  located  as  near  the  point 
where  the  feeders  enter  the  station  as  possible.  Behind  the 
switchboard  is  not  the  proper  place  for  the  lightning  arresters  as 
a  rule. 

The  panel  form  of  construction  is  now  universally  adopted,  the 
apparatus  being  mounted  on  an  upper  panel,  with  a  foot  plate  about 
twenty  inches  high  below  it.  These  panels  are  made  interchange- 
able for  the  different  units  and  feeders,  and  the  extension  of  a 
switchboard  only  requires  that  the  bus  bar  and  iron  frame  be 
extended.  This  gives  a  very  flexible  method,  and  amply  provides 
for  the  future  growth  of  the  system. 

Fig.  90  shows  an  assembly  of  a  modern  form  of  street  railway 
switchboard.  It  consists  of  an  edgewise  dynamo  regulator  "A," 
dynamo  switches  "B" — the  positive  switch  in  this  case  being  dou- 
ble throw,  as  this  board  is  arranged  for  two  potentials — field  switch 
"C,"  dynamo  galvanometers  UD"  and  amperemeters  "E,"  also 
circuit  breakers  "F."  This  panel  was  designed  by  the  author  to 
take  care  of  two  two-hundred-kilovvatt  railway  generators;  its 
width  is  twenty-six  inches,  and  all  connections  are  made  on  the 


ii 


RAILWAY   SWITCHBOARDS 


Q         Q 


f 

i 

ir 

3 

3 

I 

0 

0          /    / 

^JAS.  ^ 

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i 

S 

1 

back  of  the  board,  as  shown   in   the  side  and  rear  views.      The 
equalizing  in  this  case  is  done  at  the  generator,  and  the  copper  bus 

bars  are  supported  on 
the  back  by  cast-iron 
brackets  and  insulated 
from  them  by  marble 
blocks. 

It  is  very  useful  in 
some  cases  to  be  able  to 
separate  the  feeder  sys- 
tems, so  that  they  can 
be  supplied  by  indepen- 
dent generators,  where 
extra  demands  of  traffic 
require  a  higher  poten- 
tial to  be  obtained  on  the  congested  part  of  the  system,  in  order 
that  the  schedule  may  be  restored.  To  effect  this  result,  the  dynamo 
should  be  provided  with  a  double  throw  switch,  and  also  the 
equalizing  system  should  be  double,  and  the  equalizer  switch  double 
throw.  If  the  feeder  switches  are  also  provided  double  throw,  the 
feeders  can  be  operated  on  independent  generators  when  required. 
It  is  the  usual  practice  to  tie  all  rail  and  return  grounds  to  a 
common  negative  bus ;  but  to  reduce  electrolysis,  in  some  cases,  the 
ground  returns  which  are  tapped  directly  to  the  water  or  gas-pipe 
systems  are  brought  to  one  ground  bus,  and  the  rail  or  return 
feeders  are  connected  into  a  separate  ground  bus. 

Generators  are  connected  between  the  pipe  return  ground  and 
the  positive  pole  of  the  system,  and  the  rail  return  ground  to  the 
positive  pole  of  the  system ;  these  generators  are  maintained  at 


116 


RAILWAY  SWITCHBOARDS 

such  potentials,  that  the  pipe  systems  are  always  kept  at  a  lower 
negative  potential  than  the  rail  system,  so  that  all  sneak  currents 
will  flow  to  and  through  the  pipe  system  and  be  taken  from  the 
pipe  system  at  the  station  where  they  can  do  no  harm,  for  electroly- 
sis takes  place  if  they  leave  the  pipe  system  and  re-enter  the  earth 
in  their  attempt  to  return  to  the  station. 

In  regard  to  the  conductors  behind  the  board,  these  are  supported 
on  porcelain  insulators,  or  threaded  through  porcelain  blocks  as  a 
rule,  and  in  this  case  weather-proof  insulation  is  sufficient  for  the 
conductor  itself.  All  conductors  should  be  stranded,  and  even  the 
field  wires  should  be  a  stranded  conductor,  in  order  to  reduce  the 
hazard  that  a  solid  conductor  used  here  would  increase.  In  some 
cases  lead-covered  leads  are  used,  but  where  bare  rubber  is  used  for 
the  insulation,  great  care  should  be  exercised  to  prevent  oil  from 
reaching  these  conductors. 

The  thickness  of  the  marble  used  for  the  switchboard  surface 
should  not  be  less  than  one  and  one-half  inches  where  the  circuit 
breaker  opens  on  the  board,  as  this  blow  will  crack  thinner  marble. 
Care  should  also  be  taken  not  to  drill  too  many  holes  in  line,  either 
horizontally  or  vertically,  as  it  may  seriously  weaken  the  marble  or 
slate  through  this  line. 

Exposed  terminals  of  different  potential,  adjacent  to  one 
another,  should  be  taped  and  insulated,  or  so  shielded  that  no 
spark  can  jump  between  them,  for  when  the  circuit  breaker  opens 
on  overloads  there  may  be  quite  a  rise  in  potential  on  the  dynamo, 
which  sometimes  starts  a  flaring  arc  between  exposed  adjacent  sur- 
faces, which  may  produce  damaging  results. 

So  closely  allied  to  the  switchboard  connections  is  the  ground 
connection  of  lightning  arresters,  and  so  many  good  lightning 

117 


RAILWAY   SWITCHBOARDS 

arresters  have  been  condemned  on  account  of  their  poor  ground 
connections,  that  a  word  here  in  regard  to  this  important  point  will 
not  be  amiss.  Every  obstruction  offered  to  the  flow  of  this  dis- 
charge by  the  ground  wire  subjects  the  station  apparatus  to  an 
electrostatic  stress,  tending  to  break  it  down  at  its  weakest  point, 
and  every  means  should  be  used  so  that  the  lightning  discharge 
can  jump  the  spark  gap  of  the  arrester  and  pass  to  ground.  With 
this  high  frequency  which  a  discharge  possesses,  it  has  a  tendency 
to  travel  on  the  surface,  rather  than  on  the  interior  of  the  wire,  and 
in  this  way  choke  its  own  passage ;  this  effect  increases  as  the 
diameter  of  the  wire  increases,  and  consequently  only  a  small  wire 
is  used  for  the  ground  conductor,  No.  6  being  the  usual  size.  A 
bend  in  a  conductor  greatly  increases  its  self-induction,  conse- 
quently the  wire  should  be  as  straight  as  possible  from  the  point  of 
connection  at  the  lightning  arrester  to  the  ground  connections. 
Carrying  this  wire  parallel  to  or  near  masses  of  iron  will  also  tend  to 
retard  by  self-induction  the  passage  of  this  discharge  to  earth.  To 
use  a  water-pipe  system  for  earth  is  not  the  best  practice ;  but  where 
it  is  necessary,  a  brass  lug  can  be  clamped  to  the  water-pipe  and 
the  contact  surfaces  amalgamated ;  into  this  lug  solder  the  ground 
wire.  After  the  connection  is  made,  it  should  be  painted  over 
with  two  coats  of  air-drying  asphalt  varnish.  No  ground  connec- 
tions that  are  used  for  any  other  purpose  should  be  used  for  the 
lightning  arrester  ground.  No  part  of  an  iron  structure  or  piping 
through  the  building  should  be  used  for  the  purpose  of  this  con- 
ductor. The  ground  conductor  should  be  connected  to  the  water 
system,  as  near  its  entrance  to  the  earth  as  possible. 

A  ground  near  running  water  or  naturally  moist  earth  will  give 
the  best  results,  but  in  all   cases  it  must  be  below  the  frost-line. 

118 


RAILWAY   SWITCHBOARDS 


If  these  cannot  be  secured,  a  hole  can  be  sunk  in  the  ground  until 
water  is  reached.  A  copper  plate  two  by  two  feet,  with  the  con- 
ductor firmly  soldered  to  it,  will,  in  ordinary  cases,  be  adequate  for 
lightning  ground.  Loose  waste  metal  does  not  materially  increase 
the  actual  contact  area  of  the  earth  plate.  If  such  material  is  used 
for  the  earth  plate,  each  piece  should  be  connected  with  the  ground 
conductor  itself.  The  best  material  to  use  to  get  a  low  resistance 
ground  is  broken  coke;  this  should  be  tamped  well  in  the  bottom 
of  the  hole  to  a  depth  of  about  two  inches,  and  then  the  copper 
plate  laid  on  this,  and  about  four  inches  more  coke  laid  over  the 
ground  plate  and  tamped  well.  Dirt  can  then  be  thrown  over  this 
and  tamped  lightly. 


BACK  VIEW  OF 
SPECIAL  RAILWAY 
SWITCHBOARD  FOR 
MARIETTA  STREET 
RAILWAY, 
MARIETTA,  O. 
BUILT  AND  INSTALLED    BY 

WALKER  Co. 
CLEVELAND,  O. 


FRONT  VIEW  OP 

SPECIAL  RAILWAY 
SWITCHBOARD  FOR 
MARIETTA  STREET 
RAILWAY, 
MARIETTA,  O. 
BUILT  AND  INSTALLED  BY 

WALKER  Co. 
CLEVELAND,  O. 


ALTERNATING  CURRENT  SWITCHBOARDS 

ENERAL  features  in  the  construction  of  alter- 
nating current  switchboards,  wherein 
they  depart  in  their  designs  from  those 
already  described,  will  be  considered. 

Increasing   the  potential   brings  in  a 
hazard  to  the  attendant  which   must  be 
taken  care  of,  also  the  leakage  between 
terminals  in  a  board  designed  to  control 
over  one  thousand    volts,   if   the   marble 
itself  is  only  depended  upon  for  insula- 
tion.     All  terminals  and  screws  or  bolts 
holding  these   terminals    to  the    marble 
should  be  insulated  from  the  marble  itself 
by  mica  or  micanite,  or  an  equivalent  in- 
sulation ;  fibre  is  not  of  any  value  here,  as  it  is  a  poor  insulator  when 
under  compression.     This  method  of  insulating  will  greatly  reduce 
the  surface  leakage,  which  may  become  serious  in  damp  weather. 

All  exposed  terminals  on  the  front  of  the  board  should  be 
screened  from  the  switchboard  attendant.  Several  fatal  accidents 
have  occurred  from  the  neglect  of  this  point,  as  the  attendant  has 
fallen  against  the  exposed  terminals  with  serious  results.  If  these 
points  be  borne  in  mind,  the  alternating  current  switchboard 
becomes  very  simple  in  design. 

The  severing  of  high  potential  circuits,  when  alternating,  is  not 
so  difficult,  as  the  current  reversals  do  not  maintain  such  a  fierce 

1 20 


ALTERNATING   CURRENT   SWITCHBOARDS 

arc  between  these  switch  terminals,  as  in  the  case  of  much  lower 
direct  potentials. 

In  the  switches  used,  it  is  usual  to  place  over  them  a  marble 
slab,  having  the  free  switch  blade  in  front,  and  with  recesses  in 
this  marble  which  screen  the  clips.  Another  form  of  construction 
is  to  have  only  the  switch  handle  on  the  front  of  the  board,  and  all 
the  switch  mechanism  arranged  behind  the  board,  with  a  handle 
projecting  in  front  which  can  be  pushed  or  pulled  to  shift  the  con- 
nections from  one  side  of  the  system  to  the  other. 

Alternating  current  machines,  not.  producing  a  character  of  cur- 
rent which  will  magnetize  their  own  field,  require  separate  exciters 
and  a  separate  field  system.  Also  as  alternating  current  dynamos, 
they  are  not,  as  a  rule,  run  in  parallel ;  this  again  separates  the 
feeder  system,  so  that  each  feeder  can  be  supplied  by  any  generator. 
The  character  of  the  current  also  allows  of  regulating  devices 
which  increase  or  diminish  the  potentials  supplied  that  feeder,  by 
inserting  in  it  transforming,  regulating,  or  compensating  de-vices. 

In  long-distance  transmission,  where  high  potential  is  necessary 
in  order  to  reduce  the  copper  line  costs,  the  alternators  deliver  the 
current  at  normal  potentials  to  step-up  transformers,  which  again 
increase  the  potential  and  reduce  the  current  for  a  given  kilowatt 
output. 

All  these  characteristics  and  peculiarities  of  alternating  current 
systems  have  to  be  taken  care  of  in  the  switchboard  design, 
besides  the  different  connections  required  by  the  two-phase,  three- 
phase,  polyphase  and  monocyclic.  First  taking  up  the  field  con- 
nections and  exciting  methods  where  there  are  several  alternators, 
it  is  better  economy  to  use  one  exciter  of  sufficient  capacity  for  all 
the  alternators  than  a  separate  exciter  for  each  machine;  provid- 


ALTERNATING   CURRENT   SWITCHBOARDS 

ing  two  exciters  of  sufficient  capacity  gives  a  duplicate  exciting 
system. 

A  rheostat  is  used  in  the  exciter  fields,  and  all  the  alternators  on 
this  exciter  can  have  their  potential  raised  or  lowered  together. 
Each  alternator  is  again  provided  with  a  rheostat  in  its  field  circuit, 
.so  that  each  alternator  can  be  independently  regulated.  Where 
the  alternators  are  not  worked  in  multiple,  a  pair  of  horizontal  bus 
bars  are  used  for  each  single  phase  machine.  The  feeder  is  pro- 
vided with  a  double  throw  switch,  the  middle  clip  of  which  has  the 
feeder  connected  to  it.  The  other  terminals  are  provided  with  a 
plug  receptacle,  and  also  the  bus  from  the  generators.  In  this  way 
the  feeder  can  be  connected  to  any  bus,  or  changed  to  any  other 
dynamo  by  first  plugging  in  to  the  proper  generator  and  then 
throwing  over  the  switch  of  that  feeder.  Where  the  alternators 
are  worked  in  parallel,  only  a  double  pole  switch  is  required  for 
the  feeders,  as  alternators  are  added  as  the  load  of  the  feeders 
increases. 

In  order  to  accommodate  the  different  combination  of  phases, 
the  proper  switching  arrangements  are  shown  in  the  diagrams  for 
these  different  systems. 

In  working  alternators  in  parallel,  it  is  necessary  to  have  both 
the  potential  and  the  period  at  which  it  occurs  in  step,  in  order  that 
the  generators  may  be  thrown  together  and  work  synchronously. 
Two  generators  considerably  out  of  step  will  jump  together 
when  connected  in  multiple,  but  will  throw  considerable  strain 
on  the  armature  and  driving  mechanism.  It  is  also  evident 
that  a  potential  indicator  will  not  be  useful  in  putting  alternators 
together,  consequently  a  synchronizer  is  necessary.  Fig.  91  shows 
a  form  of  visual  synchronizer,  in  which  there  are  two  primaries, 


122 


ALTERNATING   CURRENT   SWITCHBOARDS 

one  actuated  by  the  electro-motive  force  of  one  generator,  and  the 
other  by  the  electro-motive  force  of  the  other  generator ;  each  pri- 
mary induces  an  electro-motive  force  of  fifty 
volts.  When  these  two  primaries  are  acting 
on  the  same  secondary,  and  both  currents 
are  in  phase,  the  electro-motive  force  will  be 
one  hundred  volts,  and  the  lamp  will  be 
maintained  at  full  candle-power.  The  con- 
nections usually  employed  are  those  to 
reverse  one  of  these  primaries,  so  that  the 
induced  electro-motive  forces  oppose  each 
other,  and  the  lamps  are  out  when  the 


FIG.  91 


generators  are  in  phase.  The  objection  to  this  connection 
is,  that  if  the  lamp  happens  to  break  or  the  circuit  be  open, 
the  alternators  will  be  thrown  in  when  they  are  probably  out 
of  step. 

An  acoustic  synchronizer  is  also  used,  in  which  the  currents 
from  the  two  machines  to  be  thrown  together  act  oppositely  on  a 
diaphragm.  When  there  is  a  phase  difference  between  the  two 
currents,  the  diaphragm  is  in  vibration,  but  when  the  phase  on  the 
two  machines  is  synchronous,  the  acoustic  syn- 
chronizer does  not  emit  a  sound,  as  the  attrac- 
tions are  equal  and  opposed.  Fig.  92  shows 
this  form  of  synchronizer. 

The   phase  indicator  is  an  instrument  that 
shows    the    angular    difference    which    occurs 
between  the  maximums  of  two  varying  currents. 
Fig.  93  shows  an  instrument  for  this  purpose,  in  which  the  current 
from  the  two  sources,  when  they  are  out  of  phase  with  each  other, 


FIG.  92 


123 


ALTERNATING   CURRENT   SWITCHBOARDS 

tend  to  rotate  an  armature ;  this  effort  is  proportional  to  the  phase 
difference. 

Voltmeters  for  alternating  currents  do  not,  as  a  rule,  measure 

directly  the  potentials  of  the  cir- 
cuits, but  a  transformer  is  used  with 
a  known  ratio  of  transformation, 
which  reduces  the  potential  of  the 
circuit  to  fifty  or  one  hundred  volts. 
A  voltmeter  is  connected  across 
the  secondary  of  the  transformer, 
and  the  machines  regulated  by  this 
voltmeter. 

Alternating  ground  detectors 
act  in  the  same  manner  when  one 
end  of  the  primary  is  connected  to 
the  line  and  the  other  end  to  ground;  if  there  is  any  leak  on 
the  system,  a  current  will  flow,  and  for  the  brilliancy  of  the 
lamp,  the  amount  of  external  resistance  to  ground  can  be 
judged. 

In  regard  to  conductors  used  for  alternating  currents,  ones  hav- 
ing diameter  larger  than  one-half  inch  should  be  stranded,  as 
beyond  this  size  there  is  considerable  more  drop  than  that  due  to 
the  ohmic  resistance  of  a  conductor.  Owing  to  the  tendency  of  the 
alternating  currents  to  distribute  themselves  unequally  across  a  sec- 
tion of  a  conductor,  and  flowing  more  on  the  external  surface  rather 
than  the  interior  of  the  conductor,  this  effect  decreases  as  the 
frequency  is  reduced.  Feeders  were  formerly  protected  by  fuses, 
which  were  enclosed  in  a  fuse  box  having  a  semi-circular  groove  in 
which  the  fuse  was  laid. 


FIG.  93 


124 


ALTERNATING    CURRENT   SWITCHBOARDS 

Circuit  breakers  are  now  being  used  extensively  on  the  alter- 
nators, and  afford  them  the  same  protection  which  is  so  necessary 
in  railway  practice. 

The  connections  for  the  most  prevalent  systems  used  in  practical 

work  are  shown. 

Diagram  No.  1 1  il- 
lustrates the  method  of 
connecting  a  single 
phase  system  having  a 
common  field  circuit 
and  independent  dy- 
namo circuits.  Trac- 
ing out  the  field  con- 
nections, the  current 
generated  at  the  ex- 
citer "E"  passes  to 
the  terminals  of  the 
switches  "S,"  "ES," 
and  when  this  double 
throw  switch  makes 
connection  with  the 
field  busses,  the  cur- 
rent is  returned  back 
to  the  exciter  through 
the  other  pole  of  the 

switches.  In  this  way  the  fields  can  be  operated  on  either  exciter 
and  shifted  from  one  to  the  other  without  opening  the  field  cir- 
cuits. These  connections  are  entirely  independent  of  the  arma- 
ture and  its  potentials,  one-hundred-and-ten-volt  system  being 


Diagram   NO  I  I  • 


125 


ALTERNATING   CURRENT   SWITCHBOARDS 

generally  used  for  exciting;  the  construction  of  this  part  of  the 
alternating  current  switchboard  can  be  followed  out  on  the  lines 
given  for  low  potential  switchboard  construction. 

Regarding  the  generator  terminals,  one  is  connected  to  the  cir- 
cuit breaker,  then  to 
one  pole  of  the  dou- 
ble pole  switch,  and 
carried  through  the 
ammeter  to  that  alter- 
nator's bus;  the  other 
terminal  of  the  alter- 
nator is  also  carried  to 
the  double  pole  switch 
to  that  alternator's 
bus.  In  this  system, 
each  machine  is  pro- 
vided with  a  pair  of 
busses,  extending  pref- 
erably behind  the 
board,  so  that  the 
feeders  can  be  connec- 
ted to  these  different 
busses. 

Where    only    two 


alternators  are  used, 
it  is  evident  that  double  throw  double  pole  switches  will  make  the 
proper  connections ;  but  when  more  alternators  are  used,  it  is  the 
usual  practice  to  provide  plug  terminals  on  the  horizontal  dynamo 
busses  for  each  feeder,  and  also  on  the  double  throw  feeder  switch, 

126 


ALTERNATING   CURRENT   SWITCHBOARDS 

so  that  this  feeder  can  be  plugged  into  any  dynamo;  by  having 
this  feeder  double  throw,  in  order  to  change  from  one  dynamo  to 
another,  the  idle  terminals  of  the  switch  can  be  plugged  into  the 
dynamo  to  which  this  feeder  is  to  be  transferred,  and  in  this  way  it 

can  be  shifted  quickly 
without  dipping  the 
voltage  on  the  light 
circuits. 

Voltmeters  are  gen- 
erally provided  for 
each  alternator,  and 
an  ammeter  for  each 
feeder ;  also,  where 
the  external  distribu- 
tion requires,  a  com- 
pensator is  introduced 
into  the  feeder  circuit. 
By  varying  the  in- 
ductance of  the  com- 
pensator, the  voltage 
on  the  external  sys- 
tem can  be  varied ; 
a  ground  detector 
is  also  placed  on  this 
board  with  a  multi- 
point switch,  so  that  any  circuit  can  be  tested  for  grounds. 

Diagram  No.  12  shows  the  connections  used  where  the  alterna- 
tors are  run  in  parallel ;  in  this  case  the  field  connections  are  the 
same  as  those  shown  in  Diagram  No.  n.  A  double  pole  switch 


TT   IT  HI 


127 


ALTERNATING   CURRENT   SWITCHBOARDS 

i 

can  be  used  for  the  alternators,  and  all  the  alternators  connected 
to  a  single  pair  of  bus  bars;  the  feeders  only  require  a  double 
pole  switch,  and  in  order  to  throw  the  alternators  together  a  syn- 
chronizer has  to  be  added  and  connected  between  the  alternators. 
Lightning  arresters  are 
not  shown  in  these 
diagrams';  as  they 
are  usually  connected 
to  the  feeder  at  its 
entrance  to  the  sta- 
tion. 

Diagram  No.  13 
shows  the  connec- 
tions required  by  the 
two-phase  three-wire 
system,  with  the  al- 
ternators operating  in 
.parallel,  and  Diagram 
No.  14  shows  the  con- 
nections for  a  two- 
phase  four-wire  sys- 
tem. The  connec- 
tions for  the  two- 
phase  three-wire  sys- 
tem are  the  same  as 

those  used  for  the  monocyclic  and  three-phase  systems,  the 
middle  wire  only  being  used  for  power  circuits  in  the  mono- 
cyclic  system,  and  the  two  outside  wires  for  lighting  sys- 
tems. 


128 


ARC  LIGHT  AND  SPECIAL  SWITCHBOARDS 


ISTORICALLY  the  arc  light  switchboard 
was  the  first  combination  of  apparatus  for 
the  distribution  of  current  foi  illuminating 
purposes  which  could  be  strictly  called  a 
switchboard.  The  requirements  to-day 
have  altered  very  little  the  constructional 
features  from  those  originally  installed, 
with  the  exception  that  the  number  of 
lights  carried  by  a  single  dynamo  has 
steadily  risen  as  the  art  of  insulation 
became  more  perfected,  and  to-day  a  one- 

hundred-and-fifty  lighter  is  in  practical  operation,  which  means  a 
potential  of  approximately  seven  thousand  five  hundred  volts. 

The  same  care  in  insulating  the  terminals  from  the  switchboard 
itself  has  to  be  exercised,  but  the  current  quantity  is  low  and  does 
not  produce  a  very  serious  arc  when  the  current  is  broken. 

The  arrangement  of  the  switchboard  must  be  so  flexible  that 
any  dynamo  can  be  connected  to  any  circuit,  and  any  circuits  can 
be  looped  together  on  any  dynamo.  The  general  arrangement  to 
effect  this  is  to  bring  all  dynamo  terminals  to  a  series  of  plug 
receptacles  which  align  with  all  the  lamp  circuit  terminals.  There 
are  also  transfer  busses  provided,  as  shown  in  Diagram  15.  Here 
No.  i  machine  is  connected  to  No.  i  circuit;  No.  2  machine 
operates  No.  2  and  No.  3  circuits  in  series;  No.  3  machine  plugs 
on  the  transfer  bus,  and  circuits  Nos.  4,  5  and  6  are  in  series,  and 


129 


ARC   LIGHT  AND  SPECIAL  SWITCHBOARDS 

the  end  of  circuit  No.  6  is  transferred  back  to  machine  No.  3  by 
means  of  transfer  bus.  This  shows  the  general  combinations 
required  on  a  switchboard.  A  number  of  forms  of  plugs  have 
been  devised  for  connecting  these  circuits.  Fig.  94  is  the  oldest 

type,  which  is  simply 
a  plug  with  the  dy- 
namo or  lamp  cir- 
cuit cable  directly  at- 
tached. 

Fig.  95  shows  a 
lock  form,  in  which 
the  plug  is  inserted 
between  the  spring 
and  a  notched  latch, 
for  the  purpose  of 
connecting  these  cir- 
cuits together. 

Fig.  96  is  a  plug 
only,  without  any 
connecting  cable  to 
it;  the  dynamo  ter- 
minals are  located  on 
one  face,  and  the 
lamp  terminals  on 
another  opposite  face 

about  three  inches  apart.  The  plug  is  long  enough  to  con- 
nect these  two  terminals,  it  passing  through  a  spring  bushing 
on  the  front  face  and  registering  with  a  tapering  recess  in  the 
back  face. 


130 


FIG.  94 


ARC   LIGHT   AND   SPECIAL   SWITCHBOARDS 

Fig.  97  shows  the  form  of  plug,  which,  besides  having  the  plug 
contact,   also   has   a  sleeve,   which,  when  the  plug  is 
withdrawn,  slides  over  the  exposed  plug  terminal  and 
screens  this  contact    from    the    arcing 
effect. 

The  lamp  circuit  is  provided  with 
an  ammeter,  which  generally  has  in 
connection  with  it  a  polarity  indicator, 
so  that  the  attendant  can  see  whether 
he  has  plugged  in  his  circuits  correctly. 
Each  leg  of  the  circuit  should  be  pro- 
tected with  lightning  arresters. 

The  dynamo  controller  is  gener- 
ally located  on  a  pedestal  near  the  machine  it  con- 
trols ;  but  in  small  plants  these  controllers  are 

also  assembled  on  the  switch- 
board face  with  the  rest  of  the 
apparatus.  The  general 
method  of  making  these 
switchboards  to-day  is  to  sep- 
arate the  two  potentials  en- 
tirely, the  positive  usually 
being  on  the  upper  side  of  the 
board  with  the  positive  trans- 
fer busses,  and  the  negative 
on  the  lower  side  of  the  board. 
In  mounting  these  terminals 
FIG.  96  on  the  switchboard  face,  the 

same  precautions  should  be  exercised  as  are  given  for  high  poten- 


FiG.  95 


ARC   LIGHT   AND   SPECIAL   SWITCHBOARDS 


tial  switchboards.  A  pressure  switch  is  often  used  in  connection 
with  the  arc  light  circuit,  in  order  to  determine  the  pressure  across  the 
terminals  of  the  circuit,  and  also  the  number  of  lamps  on  the  circuit. 
By  having  a  switch  arranged  so  that  one  side  of  the  voltmeter 
can  be  connected  to  ground,  the  insulation  to  ground  can  be  tested 
while  these  circuits  are  in  operation.  Only  the  highest  grade  of 

insulated  wire  should 
ever  be  used  to  make 
these  switchboard  con- 
nections, and  the  flexible 
cables  in  front  should  be 
stranded  of  wires,  not 
larger  than  twenty -two. 
There  are  a  great 
number  of  special 
switchboards  designed  to 
fulfil  special  conditions, 
but  they  are  not  so 
generally  used  as  to 
make  their  description 
of  value.  A  few  cases 
have  been  selected  to 
illustrate  this  class 
where  originality  of  design  has  been  displayed.  Fig.  98  shows  the 
accepted  form  built  for  the  Navy,  where  compactness  was  one  of 
the  essential  features.  It  was  also  important  that  any  circuit  could 
be  supplied  from  any  generator  independently. 

The  switchboard  shown  illustrates  the   arrangement  for  three 
generators  and  eight  feeders ;  the  knife  switch  employed  here  has  a 


FIG.  98 


132 


ARC    LIGHT   AND   SPECIAL   SWITCHBOARDS 

movable  blade  which  can  engage  in  the  feeder  terminal  and  be 
thrown  so  that  any  dynamo  can  be  connected  to  any  feeder.  In  this 
case  the  potentials  are  separated  on  two  sides  of  the  board — right 
and  left-r-and  the  adjacent  terminals  are  brought  very  closely 
together  on  account  of  them  being  the  same  potential.  The 

dynamos   are   connected   in   multiple 
by  the  switches  at  the  bottom  of  the 

•/ 

cut,   and  the  instruments   and   regu- 
lators are  assembled  on  another  board. 
In  the  production  of  scenic  effects, 
fine   gradations   of    illumination   are 
required,    in    order    that   the   desired 
effect  can  be  produced.    This  requires 
inserting  a  variable  resistance 
in  series  with  each  of  the  lamp 
circuits  to  be  controlled,   and 
the  regulators  are  interlocking, 
so  that  any  group  or  groups  of 
lamps  can  be  varied  together. 
Feeder  switches  and  pilot  lamps 
which  are  across  the  different 


circuits  controlled,  are  assem- 
bled  together   for  this  special 
FIG.  99  work. 

Fig.  99  shows  one  of  the  new  types  of  switchboards  designed 
for  this  purpose. 

In  alternating  current  work  the  resistance  is  substituted  by  a 
choking  coil,  which  has  a  variable  choking  effect  on  the  lamps  in 
series  with  it. 


ARC    LIGHT   AND   SPECIAL  SWITCHBOARDS 

It  has  been  the  author's  attempt  in  writing  this  essay  on 
"Modern  Switchboards"  to  give  a  practitioner's  review  of  the 
art,  and  bring  out  such  points  in  construction,  appliances  and 
connections  as  are  necessary  for  their  proper  construction  and 
design. 


CIRCUIT  BREAKERS 
AND   THEIR   USE    IN    POWER   TRANSMISSION 

BY  \V.  H.  TAPLEY 
Chief  Electrician  U.  S.  Government  Printing  Office,  Washington,  D.  C. 

Reprinted  from   The  Electrical  Engineer  by  permission  of  Mr.  Tapley  and  the  Editors 

When  the  application  of  individual  electric  motors  to  driving 
machinery  became  firmly  established  in  the  manufacturing  world, 
and  was  conceded  to  be  a  more  economical  method  of  power  trans- 
mission than  belting  with  long  lines  of  shafting,  second  only  to  the 
motor,  and  how  properly  to  connect  it  to  the  machine  which  it  was 
to  operate,  was  the  subject  of  suitable  protection  both  to  motor  and 
machine. 

The  first  thing  that  suggested  itself,  and  naturally,  was  to  pro- 
tect the  motor  in  the  same  way  as  lighting  circuits,  namely,  to 
introduce  a  suitable  fuse.  This  was  done,  and  where  motors  were 
belted  the  results  attending  overloads  were  rather  of  an  annoying 
and  aggravating  nature  than  anything  which  could  really  be  called 
serious;  yet  when  gearing  and  the  direct  application  of  armature 
to  the  main  driving  shaft  of  a  machine  began  to  supersede  the  belt, 
it  was  only  a  short  time  before  the  fact  that  a  fuse  was  not  an 
adequate  protection  became  forcibly  impressed  upon  the  advocates 
of  electrical  power  transmission. 

As  the  art  advanced,  the  thing  to  which  the  electrical  engineer 
would  turn  for  a  rational  solution  of  the  problem  was  the  electric 
current  itself.  How  well  this  has  been  accomplished  is  shown  by 


CIRCTIT  BREAKERS  AND  THEIR  USE  IX   POWER  TRANSMISSION 

the  successful  introduction  of  the  circuit  breaker,  now  so  univer- 
sally used  in  all  large  power  plants.  That  the  magnetic  property 
of  the  electric  current  was  the  means  best  adapted  for  the  actuation 
of  the  protective  device,  and  gravitation  the  most  reliable  force  for 
governing  its  operation,  is  seen  by  the  great  superiority  of  the  cir- 
cuit breaker  which  depends  entirely  upon  these  forces,  over  those 
in  which  the  effect  of  the  actuating  current  is  subject  to  variation 
due  to  extraneous  conditions. 

PROTECTION  AND  WHAT  IT  SHOULD  BE,  AS  APPLIED  TO 
A  LARGE  MANUFACTURING  PLANT 

In  treating  of  this  subject  the  tendency  of  the  engineer  has 
been  to  regard  it  almost  entirely  from  an  electrical  point  of  view, 
incidentally,  if  at  all,  considering  that  which  affected  the  real  suc- 
cess of  the  manufacturing  establishment  employing  motors,  namely, 
constant  service  and  lowest  cost  of  production.  Before  entering 
further  into  this  matter,  let  us  see  what  is  absolutely  required  to 
give  a  manufacturing  establishment  protection  worthy  of  that  name, 
when  using  electrical  power  transmission. 

First — To  secure  the  protection  of  electrical  apparatus  from 
motor  to  generator. 

Second — To  provide  a  method  which  will  afford  ample  protec- 
tion for  the  machinery  to  which  electric  motors  are  attached. 

Third — To  secure  a  freedom  from  interruption  of  production, 
and  avoid  the  exasperating  delay  which  is  experienced  in  replacing 
any  part  of  the  protective  device  after  the  same  has  been  called 
into  service. 

Fourth — After  protecting  everything  in  the  shape  of  machinery, 
the  safety  of  building  and  electrical  apparatus  and  providing 

136 


CIRCUIT  BREAKERS  AND  THEIR  USE  IN  POWER  TRANSMISSION 


against  the  stoppage  of  production,  the  mat- 
ter of  reducing  to  the  lowest  possible  point 
the  liability  of  accident  to  the  operators 
required  to  handle  either  motors  or  machin- 
ery must  be  considered,  as  indeed  this  is  a 
matter  of  supreme  importance. 

That  all  the  above-mentioned  features  are 
ever  present,  confronting  the  engineer,  who 
is  responsible  for  the  successful  operation  of 
a  manufacturing  plant,  is  confirmed  by  the 
large  number  of  so-called  protective  devices 
already  offered  to  the  public. 

At  present  a  very  large  part  of  the  labor  of 
the  electrical  engineer  and  the  manufacturers 
of  this  kind  of  electrical  apparatus  has  been 
directly  in  one  line,  that  of  protecting  the 
electrical  apparatus  from  the  effects  of  over- 
heating and  the  building  from  fires  which 
might  occur  from  heavily  overloaded  circuits. 

As  this  feature  is  commanding  a  large 
share  of  attention  in  the  electrical  press  and 
manufacturing  world,  it  would  seem  best  to 
devote  our  time  in  this  article  to  the  field 
suggested  in  the  last  three  of  the  foregoing 
propositions,  which,  if  satisfactorily  solved, 
of  necessity  cover  all  the  ground  now  under 
consideration  by  engineers,  on  the  subject 
of  proper  and  positive  protection  to  electrical 
apparatus  as  applied  to  transmission  of  power. 

'37 


CIRCUIT  BREAKERS  AND  THEIR  USE  IN  POWER  TRANSMISSION 

The  pronounced  success  during  the  past  two  or  three  years  of 
the  direct  application  of  electric  motors  to  all  kinds  of  machinery 
has  put  this  method  of  power  supply  so  far  in  advance  of  other 
methods  that,  notwithstanding  the  comparatively  high  first  cost,  it 
is  now  considered  the  most  economical  method,  and  should  be 
adopted  by  every  large  manufacturing  plant  where  the  work  is,  in 
any  sense,  of  an  intermittent  nature. 

Let  us  now  look  from  the  electrical  side  to  that  of  the  manufac- 
turing plant  proper,  and  see  if  protection  is  not  even  more  impor- 
tant and  imperative  here,  where  very  much  larger  sums  of  money 
are  invested,  and  until  now  have  been  wholly  neglected  except  by 
insurance  from  fire. 

To  suggest  something  which  may  form  a  topic  for  discussion,  let 
us  take  the  case  of  a  printing-press  to  which  is  directly  connected 
an  electric  motor.  The  cost  of  the  printing-press  is,  roughly  speak- 
ing, $3,000.00,  and  that  of  the  motor  equipment  $300.00.  (These 
are  nominal  figures,  which  vary  with  the  class  of  press  used  and 
character  of  work  required  from  it;  the  cost  of  motors  also  varies 
considerably,  but  these  figures  are  conservative  and  fully  within  the 
figures  for  which  good  apparatus  can  be  purchased.)  Allowing  the 
electrical  to  be  one-tenth  the  cost  of  the  mechanical  installation, 
does  it  not  seem  strange  that  it  has  always  been  the  motor  which  it 
has  been  the  sole  idea  of  the  engineer  to  protect,  notwithstanding 
its  cost  is  insignificant  as  compared  with  the  value  of  the  machine 
to  which  it  is  attached?  Is  it  any  wonder  that  the  manufacturers 
of  costly  machinery,  such  as  printing-presses,  have  looked  with 
doubtful  eye  upon  the  method  of  direct  motor  application,  whether 
it  be  by  gearing  or  having  the  armature  of  the  motor  keyed  to  the 
main  shaft  of  the  press?  The  manufacturer  well  knew  that  for  a 


CIRCUIT  BREAKERS  AND  THEIR  USE  IN  POWER  TRANSMISSION 

short  time  the  motor  was  capable  of  producing  perhaps  five  times 
its  rated  output,  and  realized  that  if  this  period  covered  only  a  few 
seconds,  there  was  a  great  probability  that  it  would  be  sufficient  to 
ruin  the  press  should  anything  occur  which  would  tend  to  stop  it 
suddenly.  He  did  not  feel  that  there  was  even  the  protection 
which  is  afforded  the  presses  when  driven  by  belts,  for  these  would 
slip  when  called  upon  to  do  much  more  than  the  normal  work  of 
driving  the  press. 

The  writer  takes  the  same  ground  as  the  machinery  builder,  and 
when  the  representatives  of  companies  manufacturing  electrical  appa- 
ratus were  asked  about  this  matter,  they  invariably  assured  the  pur- 
chaser that  a  fuse  inserted  in  the  circuit  supplying  the  motor  with 
current  would  provide  against  all  possible  trouble  of  this  kind.  It 
was  tried ;  the  fuse  worked  in  some  cases  and  we  began  to  take  cour- 
age, thinking  that  perhaps  we  were  too  particular  and  that  the  fuse 
afforded  the  required  protection.  It  was  seen,  however,  that  the  blow- 
ing of  the  fuse  might  serve  to  protect  the  motor  but  not  the  press. 

It  is  impossible  to  change  over  from  one  method  of  operating 
machinery  to  another  without  meeting  failures,  due  perhaps  to 
nervousness  on  the  part  of  the  operator  when  called  upon  to  do  a 
thing  for  the  first  time ;  and  certainly  it  was  so  when  motors  were 
first  used  in  this  manner.  The  sudden  turning  on  of  the  control- 
ler naturally  blew  the  fuse,  which  too  often  was  sufficiently 
increased  in  size  to  prevent  this  annoyance.  But  at  its  best  the 
fuse  served  only  to  protect  the  motor,  the  requirements  of  the 
motor-driven  machine  being  altogether  overlooked.  To  better 
appreciate  the  shortcomings  of  the  fuse  in  this  respect,  it  is  only 
necessary  to  understand  the  conditions  under  which  it  operates  to 
open  the  circuit  in  which  it  may  be  placed. 

139 


CIRCUIT  BREAKERS  AND  THEIR  USE  IN  POWER  TRANSMISSION 

The  effective  energy  which  must  be  supplied  to  the  fuse  is  made 
up  of  the  following  quantities :  First,  heat  sufficient  to  raise  the 
temperature  to  that  of  the  melting  point  of  the  fuse ;  and  second, 
an  additional  amount  of  heat  proportional  to  the  mass  and  latent 
heat  of  fusion  of  the  fuse,  while  in  addition  to  this,  the  heat,  being 
radiated  by  the  fuse  and  its  terminals,  must  be  supplied.  It  will  be 
seen  from  a  consideration  of  these  facts  that  the  fuse  requiring  a 
relatively  large  excess  of  energy  to  effect  its  operation  will  permit 
a  proportional  excess  of  power  to  be  supplied  to  the  motor.  The 
damage  which  may  result  from  this  may  perhaps  be  more  readily 
seen  by  an  example.  Suppose  a  foreign  body  gets  into  the  work- 
ing parts  of  a  machine  which  is  directly  connected  to  a  motor. 
The  power  supplied  by  the  motor  is  now  expended  in  the  wreck- 
ing of  the  machine,  the  weakest  parts  yielding  first  to  the  strain. 
Only  a  very  short  time  is  necessary  for  the  execution  of  great  dam- 
age. The  possibility  of  damage  is  then  limited  only  by  the  energy 
required  to  blow  the  fuse. 

It  was  only  upon  the  advent  of  the  modern  circuit  breaker  that 
protection  worthy  the  name  was  secured  for  motor-driven  machin- 
ery. Owing  to  the  much  lessened  energy  required  in  the  opera- 
tion of  this  device,  the  time  required,  upon  the  occurrence  of  an 
abnormal  flow,  for  the  opening  of  the  circuit  is  minimized,  while, 
in  addition  to  this,  the  heavier  overloads  are  made  to  contribute 
some  of  their  energy  to  the  acceleration  of  the  circuit-opening 
switch,  thereby  still  further  decreasing  the  time  of  opening. 

It  may  thus  be  seen  that  by  the  use  of  a  properly  constructed 
circuit  breaker  the  excess  of  power  which  may  be  communicated 
to  the  machine  is  vastly  reduced  as  compared  with  the  fuse.  In 
fact,  the  time  element  is  so  lessened  that  the  possibility  of  damage 

140 


CIRCUIT  BREAKERS  AND  THEIR  USE  IN  POWER  TRANSMISSION 

to  machine  as  well  as  to  motor  is  practically  limited  to  that  due  to 
their  combined  momentum.  What  this  is  in  each  individual  case 
makes  it  necessary  to  decide  whether  an  auxiliary  break  to  take 
care  of  the  same  is  necessary  or  not.  This  is  a  question  for  the 
mechanical  engineer  to  solve ;  but  whatever  this  may  be,  it  does  not 
affect  the  principles  set  forth  above,  and  only  serves  to  bring  out 
more  clearly  how  necessary  it  is  to  shut  off  the  current  instantly 
and  thus  prevent  the  machine  from  acquiring  any  additional 
momentum. 

As  the  question  of  machinery  protection  has  been  given  so  little 
consideration,  it  was  deemed  advisable  to  bring  to  the  reader's 
notice,  in  rather  a  minute  way,  all  the  possibilities  that  it  may  have, 
in  order  to  give  to  the  subject  the  importance  which  we  feel  it 
deserves.  In  the  foregoing,  a  reference  was  made  to  the  compara- 
tive cost  of  a  printing-press  and  that  of  the  necessary  electrical 
equipment  to  drive  the  same;  /.  e.,  $3,000.00  for  the  former  and 
$300.00  for  the  latter — a  relative  value  often  to  one,  which  justifies 
the  statement  that  the  protection  of  machinery  is  a  much  more 
important  consideration  in  electrical  transmission  than  that  of  the 
motor.  Can  the  electrical  engineer  afford  to  neglect  this  important 
feature  of  machinery  protection  and  still  hope  that  his  customer 
will  secure  satisfactory  results?  for,  after  all,  it  is  necessary  that  the 
new  system,  as  a  whole,  shall  be  made  more  productive,  and  there- 
by more  profitable,  than  the  old. 

It  may  be  assumed  that  our  third  proposition  is  intended  more 
especially  for  the  manufacturer  than  the  engineer ;  but,  taking  the 
ground  that  that  which  is  of  importance  to  the  buyer  concerns  the 
seller  also,  we  believe  it  is  worthy  of  the  close  attention  of  both. 
As  the  writer  has  had  an  extended  experience  upon  the  application 

141 


CIRCUIT  BREAKERS  AND  THEIR  USE  IN  POWER  TRANSMISSION 

of  electricity  to  printing  machinery,  he  hopes  to  be  able  to  treat 
this  branch  of  a  manufacturing  business  in  a  more  positive  manner 
than  he  could  do  should  he  endeavor  to  extend  its  scope  into  a 
more  general  or  theoretical  field. 

Referring  once  again  to  the  printing-press,  with  its  electrical 
equipment  cost  (which  we  assume  to  be  respectively  $3,000.00  and 
$300.00),  let  us  see  what  the  production  of  such  a  press  should  be 
when  it  is  running  for  three  hundred  days  in  the  year  on  a  fairly 
good  class  of  printing,  and  what  costly  affairs  stoppages  of  presses 
are,  no  matter  what  the  cause.  A  press  should  earn  an  average  of 
$10.00  a  day,  or  $3,000.00  a  year.  This  is  not  intended  to  express 
net  earnings,  but  simply  the  average  gross  earnings  for  the  press  on 
commercial  work,  and  we  assume  that  it  is  running  on  such  work 
continuously.  It  will  be  seen  that  delays  caused  by  an  accident  to 
a  press  may  prove  much  more  expensive  to  the  printer  than 
the  actual  cost  of  the  repairs  to  the  press  itself,  as  a  delay  of  a  week 
means  a  loss  of  $10.00  a  day,  or  $60.00;  and  serious  accidents 
often  mean  a  month  of  working  days,  or  $260.00,  aside  from  the 
cost  of  repairs,  which  experience  has  shown  are  not  to  be  lightly 
considered. 

Nor  is  it  to  be  forgotten  that  the  press  to  which  an  accident 
usually  occurs  is  generally  running  on  a  piece  of  work  which  must 
be  completed  within  a  given  time.  This  means  that  we  must  lift 
the  form  and  place  it  upon  another  press  which  has  to  be  "made 
ready,"  perhaps  interfering  with  other  work,  and  all  this  addi- 
tional cost  must  be  borne  by  the  manufacturer  without  any  return 
for  the  same.  Is  not  the  manufacturer  fully  justified,  then,  in 
demanding  that  his  machinery  and  output  be  equally  considered 
with  that  of  the  electrical  apparatus  in  the  matter  of  protection? 

142 


CIRCUIT  BREAKERS  AND  THEIR  USE  IN   POWER  TRANSMISSION 

If  the  protection  of  apparatus  worth  $300.00  is  deemed  so  impor- 
tant as  to  occupy,  as  it  undoubtedly  does,  the  attention  of  the  fore- 
most electrical  engineers,  are  we  not  justified  in  taking  the  position 
that  protective  devices  should  be  so  constructed  as  to  fully  protect 
the  manufacturer  at  all  points,  and  not  stop  with  the  electrical 
equipment  alone? 

By  the  use  of  the  highest-grade  circuit  breaker  now  offered  to 
the  public,  which  fulfils  in  a  very  satisfactory  manner  all  the 
requirements  thus  far  considered,  such  a  saving  may  be  made,  not 
only  to  the  motor,  but  to  the  machine  which  it  drives,  that  the  loss 
occasioned  by  stoppages  and  on  account  of  repairs  will  be  practi- 
cally eliminated,  and  the  device  will  pay  for  itself  many  times  in 
the  first  year. 

The  delays  incident  to  the  blowing  and  replacement  of  fuses  are 
perhaps  more  annoying  in  newspaper  and  publishing  offices  (where 
mails  have  to  be  met  and  where  the  time  for  the  completion  of  a 
particular  piece  of  work  is  limited)  than  in  most  classes  of  manu- 
facturing; but  in  any  case  the  saving  is  so  important  as  to  amount 
to  very  much  more  than  the  cost  of  adequate  apparatus.  Indeed, 
it  would  seem  to  be  the  best  paying  insurance  which  the  manufac- 
turer could  possibly  obtain.  Such  delays  as  we  have  been  consid- 
ering are  practically  unknown  when  the  fuse  is  replaced  by  a 
thoroughly  mechanically  and  electrically  constructed  circuit 
breaker. 

With  the  more  universal  adoption  of  the  individual  motor  in 
electrical  power  transmission  comes  also  the  question  of  protection 
to  operatives  employed  in  handling  the  machinery.  This  is  of  so 
much  importance  that  most  of  the  States  in  this  country  have 
appointed  inspectors  to  visit  all  manufacturing  establishments  and 

143 


CIRCUIT  BREAKERS  AND  THEIR  USE  IN  POWER  TRANSMISSION 

see  that  the  proper  precautions  are  used,  and  every  means  employed 
to  lessen  the  danger  to  the  employees,  of  whatever  nature  it  may  be. 
With  all  the  precaution  taken  to  prevent  accidents,  it  is  impossible 
to  do  away  with  them  entirely.  Strange  as  it  may  seem,  the  care- 
lessness or  foolhardiness  of  the  employees  themselves  is  mainly 
responsible  for  most  of  the  accidents  which  occur  to-day,  thanks  to 
the  hearty  co-operation  of  inspectors  and  employers  in  their  endea- 
vors to  make  accidents  practically  impossible.  Yet  I  know  of  noth- 
ing to  prevent  a  man  from  placing  his  hands  in  close  proximity  to 
running  gears,  and  if  he  happens  to  have  a  piece  of  waste  in  his 
hands  and  the  same  gets  caught,  the  resulting  damage  is  only  limi- 
ted by  the  quickness  with  which  the  machine  can  be  stopped. 
Several  such  cases  have  come  under  my  personal  observation,  and 
only  the  prompt  opening  of  the  circuit  breaker  prevented  very 
serious  results.  In  one  case  a  man's  fingers  were  pulled  into  a  train 
of  gears,  he  endeavoring  to  clean  the  press  while  in  motion.  His 
fingers  were  badly  jammed,  but  the  opening  of  the  circuit  breaker 
stopped  the  press  before  any  serious  damage  was  done,  and  thus 
saved  the  man  three  fingers.  Another  case  was  that  of  a  man 
who  got  his  arm  caught  between  the  two  cylinders  of  a  press.  He 
was  fixing  the  packing  on  one  of  the  cylinders  and  motioned  to  the 
feeder  to  reverse  the  press.  Instead,  she  started  it  ahead  suddenly 
with  the  result  that  his  arm  was  drawn  in  between  the  revolving 
cylinders,  and  again,  owing  to  the  instantaneous  opening  of  the  cir- 
cuit breaker  the  pressman  escaped  with  a  severely  bruised  arm, 
instead  of  crushed  bones  as  we  had  all  expected. 

These  serve  as  examples  upon  which  to  base  a  requirement  that 
protection  to  operatives  is  not  a  matter  of  minor  importance,  and 
should  not  be  put  aside  with  the  remark:  "Let  the  employees  keep 

144 


CIRCUIT  BREAKERS  AND  THEIR  USE  IN  POWER  TRANSMISSION 

their  hands  out  of  the  machinery — we  cannot  protect  everything 
and  everybody."  To  be  sure,  we  have  no  electrical  or  mechanical 
device  which  will  make  brains  for  the  ignorant  or  prevent  careless 
operatives  from  getting  hurt ;  yet  devices  can  be  made,  as  we  have 
seen,  which  reduce  the  results  of  such  carelessness  to  a  minimum, 
and  their  employment  should  become  more  general  as  the  success- 
ful operation  of  them  becomes  better  known. 

Having  thus  considered  in  detail  the  protection  demanded  by  a 
large  manufacturing  plant  using  individual  motors  as  the  method 
of  power  supply,  we  are  confronted  with  the  proposition  :  can  these 
demands  be  met  to  the  satisfaction  of  all  concerned — to  the  builder 
of  machinery,  as  well  as  of  electrical  apparatus,  and  to  the  manu- 
facturer using  them  ?  If  such  is  the  case,  what  is  the  device  neces- 
sary to  fulfil  the  requirements,  and  is  it  commercially  obtainable? 

With  reference  to  the  fuse,  we  have  only  to  read  any  of  the 
scores  of  valuable  papers  \vritten  upon  their  action  to  fully  justify 
us  in  \vriting  against  it  "not  satisfactory'  and  passing  on.  As 
the  current  itself  may  be  the  means  of  protection,  as  well  as  that  of 
propulsion,  the  method  of  opening  the  circuit  electrically  should  be 
employed.  This  has  been  successfully  accomplished  in  the  modern 
circuit  breakers  which  operate  on  the  inverse  time  element  rather 
than  the  constant  time  limit. 

The  ultimate  requirements  of  a  circuit  breaker  are  that  we  can 
rely  upon  it  to  do  all  that  we  have  shown  it  should  do,  and  operate 
successfully,  not  once,  twice,  or  for  a  month,  but  always.  When 
this  ceases  to  be  the  case,  the  magnetic  circuit  breaker  will  be 
superseded  by  some  other  means  of  protection. 

To  produce  such  an  instrument  the  highest  skill,  electrical  and 
mechanical,  is  required.  Long  study  of  the  existing  state  of  the 


CIRCUIT  BREAKERS  AND  THEIR  USE  IN  POWER  TRANSMISSION 

art  and  the  conditions  under  which  circuit  breakers  operate  is 
necessary,  and  the  closest  attention  must  be  given  to  every  detail 
of  manufacture. 

With  this  an  accomplished  fact,  such  results  are  not  the  only 
reward,  however,  nor  should  they  be.  The  public  will  cheerfully 
pay,  not  only  for  the  labor  and  material  used  in  its  production,  but 
also  a  profit  sufficient  to  encourage  the  maker  and  enable  him  to 
continue  the  work,  for  the  perfect  is  never  obtainable  and  is  only 
reached  approximately.  In  electrical  science,  perhaps  more  than 
in  any  other,  we  are  never  able  to  write  the  word  "  Finis." 


146 


THE  DEVELOPMENT  OF  THE  CIRCUIT  BREAKER 

T  is  an  old  saying  that  fire  is  a  good  servant  but  a  poor 
master — a  homely  setting  forth  of  the  broad  principle 
that  Nature's  forces  become  valuable  to  us  only  as  we 
learn  not  merely  how  to  harness  them,  but  also  how 
to  properly  restrain  them  in  harness.  In  general,  the 
more  effective  the  force  when  under  control  the  greater  the  danger 
to  be  apprehended  should  it  overcome  restraint.  In  pursuance  of 
these  principles,  it  is  seen  that  the  application  of  the  physical  forces 
to  man's  needs  is  invariably  handicapped  by  man's  inability  to  keep 
these  forces  to  their  proper  channels. 

An  illustration  of  this  is  seen  in  the  history  of  steam  engineering. 
For  many  years  after  steam  was  first  used  as  a  motive  power,  its  use 
was  restricted  to  very  low  pressures,  that  it  might  be  the  more  readily 
confined,  and  it  was  only  with  the  application  of  the  safety  valve 
and  improved  methods  of  boiler  and  engine  construction  that  the 
high  pressures  of  later  years  became  safe  and  practicable. 

The  domain  of  electricity  furnishes  us  with  another  example. 
The  one  difficulty  which  must  be  overcome  before  the  long-distance 
transmission  of  electricity  becomes  a  complete  success,  lies  in  the 
absence  of  proper  insulation,  and  it  is  only  when  this  need  shall  be 
fully  met  that  electrical  transmission  over  long  distances  will  become 
a  prime  factor  in  modern  engineering. 

These  two  instances  are  certainly  ample  warrant  for  the  state- 
ment that  the  work  of  the  engineer  consists,  not  only  in  the  devis- 
ing of  means  by  which  Nature's  forces  may  be  directed  into  the 


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THE  DEVELOPMENT  OF  THE  CIRCUIT  BREAKER 

service  of  man,  but  also  in  the  adaptation  of  further  means  to  the 
end  that  these  forces  may  be  readily  restrained  and  kept  from  effect- 
ing damage. 

As  has  been  hinted,  this  fact  is  eminently  true  in  the  domain  of 
electrical  engineering.  It  is  not  surprising,  therefore,  that  as  the 
uses  of  electricity  have  vastly  increased,  and  as  the  means  for 
employing  it  have  multiplied,  there  has  been  a  marked  development 
in  the  methods  and  devices  employed  for  the  protection  of  electric 
circuits. 

In  the  pioneer  days  of  electrical  engineering,  the  introduction  of 
strips  of  fusible  metal  into  a  circuit  was  supposed  to  afford  that  cir- 
cuit ample  protection  in  the  event  of  an  excessive  flow  of  current. 
This  device,  however,  was  only  good  enough  while  there  was  nothing 
better  to  take  its  place.  The  objections  to  this  method  of  protec- 
tion are  best  appreciated  by  those  most  familiar  with  its  results ;  for, 
aside  from  theoretical  considerations,  experience  has  taught  that  the 
melting  of  a  fuse  is  dependent,  not  simply  upon  the  passage  of  a 
certain  volume  of  current,  but  also  on  the  manner  in  which  the 
fuse  is  connected  into  circuit,  and  the  relation  between  it  and  the 
walls  and  cover  of  the  fuse  block.  In  very  many  cases  the  time 
consumed  in  the  melting  of  the  fuse,  after  the  occurrence  of  a  dan- 
gerous overload,  was  sufficient  to  allow  great  damage  to  be  done  in 
other  portions  of  the  circuit.  Further  than  this,  the  replacing  of 
fuses  involves  delays  frequently  inadmissible  in  this  age  of  haste. 
These  are  but  the  more  evident  reasons  why  the  fuse  has  given 
place  upon  the  "Modern  Switchboard''  to  the  circuit  breaker,  an 
instrument  which,  in  its  approved  form,  involves  no  such  uncertain- 
ties of  action  as  are  inherent  in  the  fuse.  Let  it  not  be  supposed, 
however,  that  the  circuit  breakers  which  were  first  introduced  pos- 

149 


I-T-E  CIRCUIT  BREAKER 

MIDGET  JR.     SINGLE  POLE.     5  TO  25  AMPERES 


THE  DEVELOPMENT  OF  THE  CIRCUIT  BREAKER 

sessed  all  the  varied  points  of  excellence  which  are  realized  in  the 
perfected  device ;  for  while  even  the  earliest  forms  offered  a  decided 
advance  over  former  methods  of  protection,  they  still  left  room  for 
improvement  in  many  respects. 

Those  familiar  with  the  first  circuit  breakers  will  remember  that 
in  their  design  the  automatic  features  were  secured  at  the  expense 
of  conductivity;  in  other  words,  a  quality  of  primary  importance 
for  normal  operation  was  sacrificed  in  order  to  provide  for  abnormal 
conditions. 

Another,  and  no  less  vital  weakness,  evident  not  only  in  the  first 
circuit  breakers,  but  also  in  many  later  forms,  was  due  to  the  fact 
that  their  operation  was  not  entirely  independent  of  everything 
save  the  actuating  current.  This  was  because  such  variables  as  the 
tension  of  springs  and  the  friction  between  metallic  surfaces  were 
allowed  to  enter  into  or  to  influence  the  adjustment  of  these  devices, 
and  naturally  resulted  in  much  uncertainty  in  their  operation. 

One  by  one,  however,  these  and  other  faults  have  been  overcome, 
and  the  circuit  breaker,  in  its  most  advanced  form,  combines  with  a 
conductivity  not  surpassed  by  that  of  the  best  switches  of  corres- 
ponding capacity,  an  accuracy  of  operation  which  compares  favorably 
with  that  of  the  best  ammeters,  and  a  certainty  of  action  compar- 
able with  that  of  gravitation  itself. 

Added  to  these  developments  there  has  been  a  vast  increase  in 
the  scope  of  the  circuit  breaker.  An  instance  of  this  is  seen  in  the 
adaptation  of  the  instrument  to  alternating  current  service.  Until 
recently  this  has  been  considered  to  be  out  of  the  question,  some  of 
the  reasons  being  that  the  earlier  forms  offered  too  great  an  im- 
pedance to  alternating  currents  of  even  ordinary  frequency,  or 
heated  unduly,  owing  to  eddy  currents  or  to  hysteresis  in  the  iron 


THE  DEVELOPMENT  OF  THE  CIRCUIT  BREAKER 

portions,  while  some  of  the  instruments  gave  rise  to  a  disagreeable 
humming  noise  when  traversed  by  the  alternating  current. 

However,  after  a  careful  study  of  the  special  conditions  involved, 
these  difficulties  were  traced  to  their  sources  and  their  remedies 
effected  by  adaptations  of  design  and  materials  to  the  peculiar 
demands  of  the  alternating  current,  resulting  in  the  production  of 
an  instrument  as  perfect  in  its  operation  as  the  better  known 
direct  current  circuit  breaker. 

Until  recently,  the  operation  of  the  circuit  breaker  has  been 
limited  to  opening  the  circuit  in  the  event  of  an  overload ;  but  in 
response  to  the  demands  of  the  ever-progressive  engineer,  there  has 
been  produced  an  instrument  which  effects  the  same  end,  upon  the 
occurrence  of  a  predetermined  minimum  flow  or  "underload." 
From  this  it  was  but  a  natural  step  to  a  combination  of  these  func- 
tions in  a  single  instrument,  resulting  in  the  production  of  a  circuit 
breaker,  operating  upon  the  occurrence  of  either  an  underload  or  an 
overload,  and  this  was  accomplished  without  a  sacrifice  of  any  of 
the  features  entering  into  either  the  efficiency  of  operation  or 
ease  of  manipulation,  which  characterize  the  simple  overload  instru- 
ment. 

The  single  pole  circuit  breaker  was  a  well-established  success 
before  a  satisfactory  double  pole  instrument  was  produced.  The 
chief  obstacle  lay  in  the  difficulty  of  obtaining  a  proper  insulation 
between  poles,  without  sacrificing  the  strength  and  the  absolute 
rigidity  necessary  on  account  of  the  automatic  action  of  the  instru- 
ment. 

Before  persistent  effort,  however,  these  difficulties  vanished,  and 
the  engineer  has  now  at  his  command  a  double  pole  circuit  breaker 
which  fully  meets  the  most  severe  requirements. 

152 


THE  DEVELOPMENT  OF  THE  CIRCUIT  BREAKER 

While  these  few  cases  indicate,  in  a  measure,  the  lines  along 
which  the  development  of  the  circuit  breaker  has  extended,  there 
have  been  improvements  of  almost  if  not  quite  equal  importance 
in  directions  other  than  those  which  have  been  cited.  The  circuit 
breaker  has  been  adapted  to  service  in  circuits  employing  the 
highest  pressures  of  ordinary  practice,  while  in  point  of  size  it  has 
been  made  to  deal  with  the  largest  and  smallest  currents  with  equal 
efficiency  and  ease.  A  whole  power  station  may  be  "opened  up" 
by  the  operation  of  a  single  massive  instrument,  or  the  circuit  of  a 
single  incandescent  lamp  may  be  automatically  broken  by  a  tiny 
device  which  may  be  covered  by  the  hand. 

To  those  familiar  with  the  development  of  electrical  apparatus, 
it  is  hardly  necessary  to  mention  that  the  continued  progress  of  the 
circuit  breaker  has  been  effected  only  at  the  expense  of  time, 
thought  and  money,  unstintingly  applied.  While  it  is  no  trifle 
in  itself,  the  circuit  breaker  largely  depends  for  its  ultimate  perfec- 
tion on  a  multitude  of  details  of  seeming  insignificance.  Even  such 
apparently  unimportant  matters  as  the  depth  of  a  contact,  the 
exact  temper  of  a  switch  blade,  or  the  diameter  of  a  bearing  pin, 
are  carefully  thought  over  and  planned,  while  the  quality,  quantity 
and  disposition  of  the  various  metals  entering  into  the  electrical 
and  magnetic  portions  of  the  instrument  are  made  the  objects  of 
careful  and  exhaustive  test.  The  designs  of  the  circuit  breaker  are 
the  outcome  of  long  experience  and  close  research,  while  the 
exactness  of  their  construction  and  the  beautiful  finish,  by  virtue 
of  which  they  enhance  the  appearance  of  even  the  handsomest  of 
"Modern  Switchboards,"  is  the  product  of  the  most  careful  work- 
manship, aided  by  the  most  improved  machinery  that  skill  can 
devise  or  money  secure.  w.  M.  SCOTT,  M.  E. 

i53 


ADVERTISEMENTS 


INDEX  TO   ADVERTISERS 


American  Circular  Loom  Company, 181 

American  Electrician, .  217 

Baker  &  Co., 199 

Bibber- White  Company, 189 

Billany  &  Cochrane 170 

Blackwell,  Robert  W. , 183,  203,  221 

Cutter  Electrical  and  Manufacturing  Company, 172,  173,  174,  177 

Columbia  Rubber  Works  Company 195 

Electric  Porcelain  and  Manufacturing  Company, 192 

Electrical  Engineer, 211 

Electrical  Review ..215 

Eynon-Evans  Manufacturing  Company, 190,  191 

Fairchild  &  Sumner 217 

General  Incandescent  Arc  Light  Company, 197 

Hansell  Spring  Company,     ....            171 

Hartford  Machine  Screw  Company, ...  183 

Hill,  W.  S.,  Electric  Company 201 

Hope  Electric  Appliance  Company, 175 

Imperial  Brass  Foundry,  Limited,      218 

Johnston,  The  W.  J.  Company 213 

Jones,  J.   &  Son, [79 

Kirkland,  H.  B.,      157 

Machado  &  Roller 187 

Merchant  &  Co.,  Inc., 219 

Murdock,  Wm.  J.  &  Co., ~.    .  209 

Moore,  Alfred   F 221 

McLeod,  Ward  &  Co., 195,  217 

New  York  Electric  Equipment  Company, 205 

Partrick,  Carter  &  Wilkins, 222 

Phosphor-Bronze  Smelting  Company,  Ltd., ...  199 

Porter  &  Remsen, 170 

Roberts,  H.  C.,  Electric  Supply  Company, 185 

Sibley  &  Pitman 221 

Solar  Carbon  and  Manufacturing   Company, 199 

Stern,  Edward  &  Co.,  Inc., 163 

Street  Railway  Journal 195 

Swoyer,  A.   P.  Company,      193 

Vallee  Brothers  &  Co 203 

Weston,  Wm.  H.  &  Co., 167 

Weston  Electrical  Instrument  Company, 158,  159,  160,  161,  162 

Wirt,  Charles 165 

Zimdars  &  Hunt, 169 

Zurn,  O.   F.   Company,      199 

156 


MR.  H.  B.  KIRKLAND 

will  be  pleased  to  extend  any 
information  required  as  to 
I-T-E  Circuit  Breakers  or 
C-S  Flush  Switches 

120  LIBERTY  ST.,       NEW  YORK 


Representing 

The  Cutter  Electrical  and  Mfg.  Co. 
American  Circular  Loom  Co. 


'57 


WESTON 
INSTRUMENTS 


THE  WESTON  ELECTRICAL  MEASURING  INSTRUMENTS 
created  a  new  epoch  in  the  art  of  electrical  measurement. 
They  were  the  FIRST,  and  remain  the  ONLY  instruments   which   fulfil   all   the 

requirements  of  the  Electrical  Engineer,  the  Station  Manager,  and  others  engaged  in 
the  electrical  business. 

Since  their  first  introduction  to  the  electrical  fraternity,  ten  years  ago,  their  use  has 
steadily  extended  to  all  parts  of  the  civilized  world,  and  they  are  now  used  and  recognized  as 
standards  for  all  classes  of  work. 

We  have  constantly  endeavored  to  improve  upon  the  original  models,  and  have  steadily 
made  advances  in  methods  of  production,  in  details  of  construction  and  in  electrical  and 
mechanical  design,  until  at  present  our  instruments  are  vastly  superior  in  all  points  to  our 
earlier  types. 

We  have  also  constantly  added  to  the  variety  of  styles  and  ranges,  and  have  developed 
new  forms  suitable  for  all  classes  of  work,  until  we  now  produce  no  less  than  one  thousand  dif- 
ferent styles,  ranges  and  models,  and  we  are  adding  to  our  lines  as  rapidly  as  this  can  be  done, 
considering  the  great  labor  and  careful  scientific  investigation  required  to  produce  really  trust- 
worthy electrical  measuring  instruments. 

We  are  original  workers  in  this  special  branch,  as  is  evidenced  by  Mr.  Weston's  discov- 
eries of  the  negligible  temperature  coefficient  alloys  and  standard  elements  ;  and  all  our  work 
is  of  a  class  distinguished  for  its  excellence  of  construction,  adaptation  to  its  special  purposes, 
and  originality  of  conception. 

We  consider  the  interests  of  your  customers  and  desire  to  serve  them  faithfully,  and  our 
effort  has  been  to  build  up  a  solid  business  to  stand  for  all  time,  and  doing  this,  we  have  put 
more  money  into  original  work,  and  in  special  tools  and  plant  for  the  production  of  high-class 
electrical  measuring  instruments  than  any  other  concern  in  the  world. 


•  •  •  Weston 
Electrical  Instrument  Co. 


114  to   120  WILLIAM  STREET 
NEWARK,   NEW  JERSEY  .  ,  . 


158 


Weston 
Instruments 


WESTON  STANDARD  ILLUMINATED  DIAL  STATION  AMMETER,   HALF  SIZE 

THE  ILU'MIXATED  DIAL  STATION  AMMETERS  AND  VOLTMETERS   are   accurate,   reliable   and   economical 
to  operate. 
The  Ammeter  is  connected  to  a  special  alloy  shunt,  separate  from  the  instrument,  and  placed  at  the  back  of  the  switch- 
board, or  a  short  section  of  the  mains  may  be  used  instead.     Only  very  small  wires  are  required  to  connect  the  instrument  to 
the  shunt.     There  is,  therefore,  a  great  saving  in  copper  and  labor  in  installing  over  other  instruments,  where  it  is  necessary  to  carry 
the  whole  of  the  working  current  to  and  from  them.     These  facts  should  be  taken  into  consideration  in  connection  with  the  price. 
If  at  any  time  the  capacity  of  the  station  should  be  increased  beyond  the  capacity  of  the  instrument,  all  that  would  be 
required  would  be  to  have  it  readjusted,  since  by  its  construction,  the  same  instrument  can  be  made  suitable  for  any  range. 
The  Voltmeters  are  very  high  resistance  instruments,  and  are  consequently  extraordinarily  economical  of  power. 
These  instruments  have  no  "  magnetic  lag,"  are  very  "  dead-beat,"  and  are  extremely  sensitive  and  accurate.     They  can  be 
left  constantly  in  circuit  with  no  material  change  in  correctness. 

The  working  parts  are  inclosed  in  an  iron  case,  which  effectively  shields  the  instruments  from  disturbing  influences  of  external 
magnetic  fields. 

WESTON  ELECTRICAL  INSTRUMENT  CO. 

114  WILLIAM  STREET,  NEWARK,  NEW  JERSEY 


Weston 
Instruments 


T 


WESTON  STATION  VOLTMETER,  "ROUND  PATTERN,"  HALF  SIZE 

HESE  instruments  are  identical  in  the  principles  of  their  construction  with  the  Illuminated  Dial  Switchboard  Instruments. 

The  scales  are  shorter,  and  being  drawn  on  opaque  paper  cannot  be  illuminated  from  the  rear.     They  are  the  same  in 
accuracy  and  reliability,  and  are  also  enclosed  in  iron  cases. 

For  large  plants,  no  type  of  switchboard  construction  possesses  so  many  advantages  as  the 

VAN  VLECK  EDGEWISE  SYSTEM. 

This  saves  enormously  in  FIRST  cost  o  constiuction  and  erection,  owing  to  the  very  small  space  required  for  the  whole  of  the 
regulating,  controlling  and  indicating  devices.  It  also  saves  much  labor  in  SUPERVISION  and  OPERATION. 

It  is  the  most  convenient  and  easiest  to  manipulate,  and  closer  regulation  can  be  much  easier  maintained  by  its  use  than  by 
any  other  system. 

It  facilitates  the  keeping  of  accurate  output  records,  and  reduces  risks  of  error,  as  well  as  reduces  costs. 

We  are  sole  licensees  under  the  patents  of  Mr.  Van  Vleck  and  Mr.  Weston,  for  the  manufacture  of  all  instruments  for  use 
with  this  system. 

We  strongly  recommend  the  adoption  of  this  system  in  all  large  plants,  and  it  can  be  used  in  small  insinuations  with  great 
advantage. 

We  make  a  full  line  of  instruments  adapted  to  the  requirements  of  the  system. 

WESTON  ELECTRICAL  INSTRUMENT  CO. 

114  WILLIAM  STREET,  NEWARK,  NEW  JERSEY 


1 60 


Weston 
Instruments 


In  addition  to  instruments  shown  in  the  fore- 
going pages,  we  furnish  the  following  for  use 
on  switchboards  : 


POTENTIAL  INDICATORS 


GROUND  DETECTORS 


WESTON  ELECTRICAL  INSTRUMENT  CO 

114  WILLIAM  STREET,   NEWARK,   NEW  JERSEY 

161 


Weston 


Our  STANTDARD  PORTABLE  INSTRUMENTS  are  all  remarkably  accurate, 
constant  and  reliable.  They  are  all  direct  reading,  are  practically  "dead-beat," 
and  can  be  kept  constantly  in  circuit  without  injury  or  change  in  accuracy. 

Below  we  show  illustrations  of  a  few  of  the  different  styles  of  portable  instruments  we  are  manu- 
facturing : 


DIRECT  CURRENT  VOLTMETER 


DIRECT  CURRENT  MTLLI-VOLTMETER 


ALTERNATING  AND  DIRECT  CURRENT 
VOLTMETER 


DIRECT  CURRENT  AMMETER 


DIRECT  CURRENT  MILAMMETER 


WATTMETER 


WESTON  ELECTRICAL  INSTRUMENT  CO. 

114  WILLIAM  STREET,  NEWARK,  NEW  JERSEY 


162 


Gdward  Btcrn  &  Co, 


Inc. 


offer  the  services  of  a  plant  capable 
of  producing  all  varieties  of  fine  book 
printing,  and  the  knowledge  and  ex- 
perience which  assure  the  highest 
accuracy  and  quality*  Personal  at- 
tention is  given  to  the  typography, 
binding,  illustrations  and  the  other 
important  details  of  bookmaking. 
Estimates  and  suggestions  will  be 
furnished  by  mail  or  a  representa- 
tive upon  application  /*  /*  <*  <#  /* 


1 1 2=1 14  ]>f .  Cwclf th  St,  Philadelphia 


163 


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The  Wirt  Dynamo  Field  Rheostat 

REPORT  OF   TEST 
LABORATORY  OF  QUEEN  &  CO.,  PHILADELPHIA,  February  28,  1898 

We  append  report  on  Wirt  Rheostat,  circular  pattern,  single  disc,  12"  diameter,  Catalogue 
No.  H22,  catalogue  rating  187  watts.  We  understood  your  instructions  to  test  at  five  times 
the  rated  capacity  in  watts,  with  full  resistance  in  circuit.  Load  to  be  thrown  suddenly  on  cold 
rheostat. 

Start          30  min.          60  min. 
Thermometer  (bulb  in  outside  contact  merely),        7o°F.  370  400 

Watts  on  rheostat 1080  1190  1230 

Watts  per  square  inch, 4.8  5.3  5.5 

Overload  (ratio  to  catalogue  rating) 5.77  6.30  6.50 

Insulation  after  test,  hot,  1.6  megohms.  After  cooling  to  212°,  5.4  megohms.   Cold,  64.5  megohms. 

General  Condition  after  test,  O.  K. 

Remarks : — Case  of  rheostat  hot  enough  to  scorch  paper  and  to  melt  solder. 

QUEEN  &  CO.,  Inc. 

P.  A.  M. 


Cast  Iron  Shell 
BS^Mica  Insulation 

German  Silver  or  Nickel  Alloy  Resistance 
Joints  in  Resistance  Conductor 


Heavy  Brass  Switch  Sectors 
Phosphor-Bronze  Contact  Lever 
Polished  Bronze  Wheel  and  Plate 
Fifty  Steps  on  Smaller  Sizes 


One  Hundred  on  Larger  Sizes 

CHARLBS    WIRT 


Send  for  description  and  prices 


1028   Filbert  St.,   Philadelphia 


165 


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THE  Switchboard  illustrated  on  the 
adjoining  page,  installed  in  the  engine 
room  of  Stephen  Girard  Building,  Twelfth 
and  Girard  Streets,  Philadelphia,  control- 
ling the  electric  light  and  power  equip- 
ments of  both  the  Stephen  Girard  Building 
and  that  of  N.  Snellenburg  &  Co.,  Twelfth 
and  Market  Streets,  was  designed  and 
erected  bv 

tf 

WM.  H.  WESTON  &  CO. 

ELECTRO-MACHINISTS  AND  ENGINEERS 

Keystone  Spring  Works  Building 

Thirteenth  and  Buttonwood  Streets 

Philadelphia,  Pa. 


167 


TELEPHONE  BUILDING  WESTERN  ELECTRIC  co. 

NEW  YORK  CITY  ENGINEERS  AND  CONTRACTORS 


The   Modern    Switchboard  Builders 

...OF  AMERICA... 

ZIMDARS  &  HUNT,  of  New  York 

T)esire  to  call  attention  to  the  fact  that  it  is  never  necessary  to  specify  as  to 

quality  when  dealing  with  them,  as  it  will  continue  to  be  their  policy  in  the  future, 

as  it  has  been  in  the  past,  to  manufacture  only  from  the  most  approved  designs, 
with  the  most  skilled  mechanics  obtainable,  and  using  only  the 
best  grades  of  materials  the  market  affords. 

SWITCHES  that  are  models  of  excellence,  correct  in  design, 
accurately  and  carefully  made,  and  embodying  the  results  of 
an  extended  experience  in  switch  manufacture. 

SWITCHBOARDS  that  are  too  well  known  to  require  com- 
ment. The  finest  that  skill  can  produce.  They  never  fail  to  an- 
ticipate the  specifications  of  the  most  progressive  engineers. 

PANEL  BOARDS  without  an  equal; 
easily  in  the  lead  for  correct  design,  su- 
perior workmanship,  and  beauty  of  ap- 
pearance; will  show  off  to  advantage  any- 
where;  a  credit  to  any  installation,  and 
AUTOMATIC  SWITCHES  AND  AUTOMATIC 
MOTOR  STARTERS,  devices  which  have 

met  with  the  most  unqualified  indorsement  of  all  parties 

having  any  acquaintance  with  them.     They  are,  beyond 

a  doubt,  the  most  approved  articles  of  their  kind  ever 

offered,  suitable  for  elevator,  pump,  crane,  organ  and  all 

other  work  where  automatic  starting  is  desired.    Made  for  direct  or  alternating 

circuits.    Absolutely  reliable  in  every  respect. 

ZIMDARS  &  HUNT 

MAKERS  OF 

High- Grade  Electric  Light  and  Power  Specialties 

127  FIFTH  AVB.,  NEW  YORK 

169 


PORTER  & 


CONTRACTORS 

39  Coftlandt  St. 


Complete  Steatn-Power  Equip- 
ment, High-Grade  Engines  for 
Electric  and  Manufacturing 
Plants,  Nordberg  Corliss  En- 
gines and  High-Duty  Pumping 
Machinery.  Special  Valve  Gear 
for  high  speeds. 

Gas  and  Air  Compressors. 
Milwaukee  Feed-WaterHeaters. 


Fischer   Automatic    High-Speed   En 
gines,  Single  and  "4  "-Valve  for 
Belted  and  Direct  Connected  work. 

"  Buffalo  "  Steam  Pumps. 
Nordberg  Jet  and  Surface  Condensers. 
Nordberg  Automatic  Governors. 
Walker's  Metallic  Piston  Rod  Packing. 


INFORMATION  AND  ESTIMATES 
FURNISHED  ON  APPLICATION 


Write  \is  when  ill  Hie  market 
for  Machinery 


BILLANY  &  COCHRANE 

DEALERS  IN 

mi^'  Toolg,  Light  Iran  and  Wood  Wooing  Tools 


BLACKSMITHS'  AND  JEWELERS'  TOOLS 
Belting,  Packing,  Hose,  Bolts,  Nuts,  Washers  and  Screws  of  all  Kinds 

527  COMMERCE  ST., 

TELEPHONE  1538 
170 


SPRING  Co. 


,  N-  *J. 


OF 


foailuuay  and  fHachinepy 


Springs... 


..OF.. 


Crucible  Cast  Steel 


Special  Springs  of  Piano 

for  severe  and  unusual  service 

171 


The  C=S  Automatic  Switch 


T 


IHE  popularity  of  this,  the  only  reliable  automatic 
switch,  is  constantly  increasing.    It  is  specially 
adapted  for  DARK  CLOSETS,  TOILET  ROOHS, 
etc.   For  this  purpose  it  is  set  flush  in  the  rabbet  of  a 
door=jamb  in  a  manner  similar  to  the  well=known 
burglar=alarm  spring.  It  is  strictly  automatic.   Open= 
ing  the  door  turns  the  light  on,  while  closing  the  door 
turns  the  light  off. 

The  Switch  is  also  made  with  a  "  reverse  action," 

i.  e.,  opening  the  door  turns  the  light  off,  while  closing  the  door  turns 
it  on. 

Another  valuable  application  of  the 
C-S  Automatic  Switch  is  shown  here, 
wherein  it  is  so  arranged  as  to  positively 
turn  off  the  electric  lights  from  a  hotel 
guest-chamber  every  time  a  guest  leaves 
his  room  and  locks  his  door  from  the 
outside. 

It  is  estimated  that  fully  ninety  per 
cent,  of  all  hotel  guests,  upon  leaving 
their  rooms,  invariably  leave  their  lights 
turned  ou,  and  in  a  hotel  of  ordinary  size 
only,  this  means  a  waste  of  thousands  of 
dollars  annually.  This  arrangement  of 
the  automatic  absolutely  prevents  such 
waste,  thus  adding  so  much  each  year  to 
business  revenue. 

The  plan  of  application  and  operation  is  simple  in  the  extreme,  as  may 

EXPLANATION. 

All  modern  hotel  guest-cl.atnbers  are  fitted  with  "secret  "  or  double-bolt  locks,  one  bolt  being  operated  from 
the  outside,  the  other  from  the  inside  of  the  door. 

For  this  service  of  economy  a  C-S  Automatic  is  placed  in  the  moulding  of  the  door-jamb,  immediately  back  of 
the  striker  plate  of  the  lock,  in  such  manner  that  the  throw  of  the  bolt  which  locks  the  door  from  the  outside 
opens  the  switch  and  turns  off  the  light,  while  unlocking  the  door  from  the  outside  turns  on  the  light.  At  the 
same  time,  locking  the  door  from  the  inside  has  no  effect  upon  the  action  of  the  switch.  Arranged  in  this  way, 
the  automatic  acts  as  the  controlling  switch  for  the  room  circuit,  and  locking  the  door  from  the  outside  will 
invariably  turn  off  the  lights. 

The  Cutter  Electrical  and  Mfg.  Co. 

PHILADELPHIA  AND  NEW  YORK 


O' 


be  seen  from  the  following 


Switches    and    Accessor- 
ies, consult  our  catalogue. 


172 


ABOUT  MARCH    IST 


WE  WILL  BEGIN  TO  DELIVER  ON  ALL  ORDERS  OUR 


NEW   AND 


PERFECTED 


C-S  SWITCH 


THE 

STANDARD 

FOR 

HIGH-GRADE 

WORK 


THE 
FIRST 

FLUSH  SWITCH 

ON  THE 

MARKET 


THIS  SWITCH,  AS  is  INVARIABLY  THE  CASE  WITH  AN  ARTICLE  WITH  AN  ESTABLISHED 
REPUTATION,  HAS  SERVED  AS  A  COPY  FOR  NUMEROUS  IMITATIONS,  CHEAP  AND  OTHERWISE. 
BEWARE  OF  THEM.  THEY  DO  NOT  STAND  THE  TEST  OF  TIME,  AND  ARE  VERY  COSTLY. 

RECENT  CHANGES  IN  THE  C-S  SWITCH  MAKE  IT 
BETTER  THAN  EVER.  THE  "PUSH"  HAS  BEEN 
MADE  EASIER  AND  THE  FORM  OF  THE 
SPRING  CHANGED  SO  THAT  BREAKAGE  OF 
THIS  PART  IS  PRACTICALLY  IMPOSSIBLE. 

THE  CUTTER  ELECTRICAL  AND  MFG.  CO. 


NEW  YORK,  120  LIBERTY  ST. 


PHILADELPHIA,  1112  SANSOM  ST. 


I-X-E   MOTOR   STARTER 

A  combination  consisting  of  the  usual  means  of  closing  circuit  with  gradually  decreasing  resistance,  with  a 
DOUBLE  POLE  AUTOMATIC  CIRCUIT  BREAKER  connected  therewith,  the  circuit  breaker  being  spe- 
cially designed  to  AUTOMATICALLY  open  the  circuit  upon  a  predetermined  OVERLOAD  or  SHORT- 
CIRCUIT  ;  also  to  OPEN  CIRCUIT  AUTOMATICALLY  IN  CASE  THE  CURRENT  SUPPLY  IS  CUT 
OFF.  AUTOMATIC  means  to  PREVENT  THE  CLOSING  OF  CIRCUIT  BREAKER  UNLESS  THE  RE- 
SISTANCE IS  ALL  IN.  The  resistance-controlling  arm  to  be  operated  MANUALLY,  as  opposed  to  the 
usual  automatic  methods  employed  ;  the  spring  part  of  this  arm  being  used  only  to  prevent  the  same  from 
remaining  on  any  of  the  intermediate  resistance  contacts.  All  contained  in  one  device. 

The  Cutter  Electrical  and   Mfg.   Co.,  1112  Sansom  Street,  Philadelphia 

174 


nni       r^  o  o      |>;JE  9NI 

1  lie  L-o  owitcli 

IS  THE  STANDARD  FOR 
HIGH-GRADE  WORK.  It  is 
the  only  flush  switch  with  an  estab- 
lished reputation.  Recent  improvg- 
ments  make  it  better  than  ever. 


HE  contact  brush- 
es are  of  the  high- 
est grade  of  phos- 
phor-bronze ;  the 
form   of  spring  has  been 
changed,  making  breakage 
of  this  part  impossible,  at 
the    same  time  rendering 
the   "push"    easier.     The 
best  quality  of  steel  piano  wire  is  used  in  the  spring,  and  ALL  THE 

INTERIOR   WORKING   PARTS   ARE    COPPER-PLATED,    thus   doill^ 

with  the  possibility  of  rusting. 

The  C-S  Switch  is  made  in  single  pole,  double  pole,  three- wire 
and  four-wire  commutation,  all  of  the  same  size  and  form.  It  is 
encased  in  a  hard,  vitreous,  non-absorbent  porcelain,  making  it 
entirely  fire-proof.  It  has  the  endorsement  of  all  Boards  of  Fire 
Underwriters. 

The  body  of  the  switch  is  recessed  into  the  wall,  with  only 
an  ornamental  face-plate  projecting.  By  the  arrangement  of  the 
button,  the  condition  ..of  a  distant  lamp,  whether  lighted  or  not, 
may  be  JtolfLatta  -.glance^  u«fe™ 

Any  number  of  switches,  in  any  combination,  may  be 
mounted  on  a  single  plate.  The  switch  plate,  usually  of  polished 
nickel  or  brass,  can  also  be  furnished  in  bronze,  silver,  or  any  of 
the  more  elaborate  finishes,  to  match  the  surrounding  hardware. 

The  C-S  "Automatic"  is  a  smaller  switch,  designed  to  be 
placed  in  the  jamb  of  a  door.  By  reason  of  its  construction,  the 
opening  of  the  door  turns  on  the  light,  or  vice  versa. 

It  has  been  brought  to  our  notice  that  contractors,  where  flush 
-witches  are  specified,  frequently  use  an  inferior  switch,  which 
does' hot  have  the  characteristics  wriicb  led  to  the  specification  of 
our  switch.  In  drawing  specifications  besurecincimentioSCne 
"C-Sv"  which  will  insure  its  use  and  prevent  annoyancet-and 
subsequent  expense.  A  complete  catalogue  with  prices 
:it  upon  •  cquest. 

•THE  CUTTER  EL,      .*&$&&%&& 
1 1 12  Sansom  Street,1  Philadelphia 
1 20  Liberty  Street,  New  York  175 


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INSTANTANEOUS  "MAKE  and  BREAK 

SAFETY  KNIFE  SWITCHES 


tt 


Extract  from  the  Rules  and  Requirements  of  the 
National  Board  of  Fire  Underwriters 

RULE  43. 

SEC.  F.  Must,  for  constant  potential  systems,  have  a  firm 
and  secure  contact ;  must  make  and  break  readily,  and 
not  stop  when  motion  has  once  been  imparted  by  the 
handle. 

WE  ARE  THE  ONLY  SWITCH-MAKERS  WHO 

FULLY  COMPLY  WITH  THE  ABOVE  RULE 


»** 


Series  Circuit 
Arc  Cut-Out 


MAST  ARMS 
POLE  STEPS 

CABLE  CLIPS 
Four  Pole  Alternating;  Current  Cut-Outs 

Indestructible  Arc  Lamp  Hanger  Boards 

**** 

HOPE  ELECTRIC  APPLIANCE  CO. 

PROVIDENCE,  R.  I.,  U.  S.  A. 


'75 


SMITH  &  CONANT 
ELECTRICAL  CONTRACTORS 


HARPER  HOSPITAL 
DETROIT,  MICH. 


INSTALLED  BY 

MICHIGAN  ELECTRIC  CO. 

DETROIT,  MICH. 


Office  of  Electrical  Construction  Division 

of  Public  Buildings  Department, 


OLD  COURT  House 

ROOM  7,  FIRST  FLOOR. 


Nov.  8th, 


7. 


Cutter  Elec.  and  Mfg.  Co. 
GentlemenI 

It  gives  me  great  pleasure  to  notify  you  that  the  special 

"double  pole  Circuit  Breakers,  which  you  built  for  the  Boston  City  Hospital 
switchboard,  have  proved  their  value  under  a  rather  unexpected  test. 
Last  Wednesday  evening  one  of  our  men  accidentally  dropped  his  wrench 
across  the  bus  bars  of  a  large  tablet  board,  completely  short-circuiting 
one  side  of  the  three-wire  system,  which  is  balanced,  by  a  5  K.  W.  Motor 
Generator.   The  Circuit  Breaker,  which  was  set  at  300  amperes,  opened 
instantly,  even  before  a  50  ampere  fuse  on  the  5  K.  W.  unit  could  act. 
Had  there  been  no  Circuit  Breaker,  we  should  have  lost  our  motor  generator, 
and  consequently  the  whole  system.   No  damage  resulted  to  the  5  K.W.  unit, 
which  had  to  deliver  current  sufficient  to  open  the  Circuit  Breaker,  and 
we  suffered  no  interruption  of  service  except  on  this  one  feeder. 
Your  Circuit  Breaker  is  ALL  RIGHT. 

Yours  truly, 


Engineer. 


GEORGE  H.  PRIDE 
ENGINEER  AND  BUILDER 


EQUITABLE  BUILDING 
NEW  YORK  CITY 


HIGH-GRADE  SWITCHBOARDS 

PANEL  BOARDS  AND 

SWITCHES 


QME  PLANTS,  IN  AND  NEAR 
NEW  YORK,  FURNISHED  WITH 
*  OUR  APPARATUS  *  *  #  *  * 


Proctor's  Pleasure  Palace,  New  York  City 

New  York  Orthopaedic  Hospital,  New  York  City 

Dakota  Apartments,  New  York  City 

Manhattan  Electric  Light  Company,  New  York  City 

United  Bank  Building,  New  York  City 

National  Meter  Company,  New  York  City 

Hotel  Waldorf,  New  York  City 

Staten  Island  Rapid  Transit  R.  R.  Station,  St.  George,  S.  I. 

Midland  Beach  Casino,  St.  George,  S.  I. 

Clarendon  Hotel,  Brooklyn 

Pratt  Institute,  Brooklyn 

F.  Loeser  &  Co. ,  Brooklyn 

Crocker  Wheeler  Electrical  Company,  Ampere,  N.  J. 

Hudson  Electric  Light  and  Power  Co.,  Hoboken,  N.  J. 

Jersey  City  Electric  Light  and  Power  Co.,  Jersey  City,  N.  J. 

Washington  Light,  Heat  and  Power  Co.,  Washington,  N.  J. 

Nepera  Chemical  Co.,  Nepera  Park,  N.  Y. 


J.  JONES  &  SON, 
67  CORTLANDT  STREET, 
NEW  YORK  CITY    FACT&LYN 


179 


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CONDUIT 


INSTALLED    WITH 
FLEXIBLE    CONDUIT 


CLIFF  HOUSE,  SAN  FRANCISCO,  CAL. 


MANUrACTURCD  fW 


AMERICAN  CIRCULAR  LOOM  CO. 


CHELSEA,  MASS. 


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ROBERT  W.  BLACKWELL 

39  VICTORIA  STREET,  W. 

LONDON,  ENGLAND 

Engineer  and  Contractor  for 
Electric  Tramway  Construc- 
tion and  Equipment 

Poles,  Trolley  Wire,  Feeders,  Rail-bonds,  Insulators,  Trolleys, 

Motor  Trucks,  Engines,  Line  Material  and  Supplies. 

I-T-E  Circuit  Breakers. 


JANUFACTURERS  of  all  classes  of  bind- 
ing pests,  with  screws,  nuts  and  washers 
for  the  same  ;  also  magnet  cores  and 
all  other  turned  parts  for  electrical  work 
not  requiring  stock  more  than  2>£  inches  in  diam- 
eter. Hexagon,  square  and  round  head  cap  and  set 
screws,  from  all  kinds  of  material.  All  small  turned 
parts  for  bicycles,  guns,  pistols,  clocks,  eye-glasses, 
watches,  etc.,  etc.  German  silver,  silver  and  gold 
screws  made  to  order.  We  are  headquarters  for 
automatic  machinery  for  producing  all  classes  of 
turned  work  ;  also  automatic  and  hand  machines 
for  finishing  operations. 

SEND  FOR  CATALOGUE  AND  PRICE  LIST 


flincjiiiiE  SCREW  co. 


,  Conn.,  U.S.A. 


183 


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H.C.ROBERTS 
ELECTRIC 
SUPPLY  CO. 


•»  f  *  *  * 


»»»»»The 

Highest  Class 
Goods  at  the 
Right  Prices** 


831  ARCH  STREET 
PHILADELPHIA 


185 


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Whitney 
Instruments 


STANDARD  A.  C.  SWITCHBOARD 
Volt-  and  Ammeter 


STANDARD  D.  C.  SWITCHBOARD 
Volt-  and  Ammeter 


MAC  HA  DO  &  ROLLER, 

SELLING    AGENTS, 
2O3  BROADWAY,  NEW  YORK 


PORTABLE  D.  C. 
Voltmeter 


PORTABLE  D.  &  A.  C. 
Ammeter 


PORTABLE  D.  C. 
Ammeter 


PORTABLE   TESTING   SET 
With  or  without  Battery 
Range  i  to  5.000,000  Ohms. 


D.  &  A.C.    SWITCHBOARD— Indicators 


D.  &  A.  C.  ELECTROMAGNET 
Switchboard  Insts. 


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Modern  Switchboards 

WE  HAKE  A  SPECIALTY  OF  ALL  HODERN 
ELECTRICAL  APPLIANCES 

Electric  Lighting 
Electric  Railway 
Electric  Power 

APPARATUS  AND  SUPPLIES 

We  Build  and  Equip  Complete  Electric  Light 
Plants,  Electric  Railway  and  Power  Plants 


BIBBER=WHITE  COMPANY 

49  Federal  Street,  Boston 


189 


1517=1523  Clearfield  St. 


Philadelphia,  Penna. 

.  .  Long  Distance  Telephone  .  . 

MACHINE  SHOP  AND  ENGINEERING 

.  .  DEPARTMENT  .  . 

We  invite  correspondence  and  will  cheerfully  furnish  estimates  on  Electrical,  Steam 

and  Hydraulic  Specialties 


SEND  FOR  NEW  CATALOGUE  OF  THE 


SPECIALTIES 


Injectors,  Blowers,  Exhausters,  Ventilators,  The  "Old  Reliable 
Steam  Trap,  Jet  Condensers,  Syphons  and  Extra  Heavy 
Globe,  Angle  and  Check  Valves  J-4  to  20  in. 


Started,  Regulated,  Stopped 
with  One  Handle 


Balanced  Regulating  Valves 

Automatic  Free  Exhaust  Valves 

The  best  for  Marine,  Locomotive  and 
Stationary  Boilers 


Takes  water  at  a  tempera- 
ture of  J50  degrees  and  requires 
no  adjustment  for  steam  press- 
ures  varying  from  J  5  to  300  Ibs. 


TO 

BOILER 


WILL  UFT  WATER  24  FE£T 


EYNON=KORTING  COMPOUND   INJECTOR 

190 


i5I7=I5:23  Clearfield  St. 

Philadelphia,  Penna. 

.  .  Long  Distance  Telephone  .  . 


COPPER,  BRASS  AND  BRONZE 
FOUNDRY  DEPARTMENT 


PURE  COPPER  CASTINGS 

Of  highest  conductivity,  sound  and  free  from  blow-holes,  easily  worked 


RED  and  YELLOW  BRASS  CASTINGS  of  every  description,  light 

or  heavy,  clean,  smooth  and  accurate  to  pattern 

Switchboard  Castings  a  Specialty 


High-Grade  Bearing  Metals  for  Engines,  Motors,  Dynamos,  Etc. 
PHOSPHOR  and  MANGANESE  BRONZE 


PATTERN  WORK  in  all  its  branches 

WRITE  FOR  ESTIMATES . 


191 


THE  ELECTRIC  PORCELAIN 

AND  MEG.  CO. 


ELCXTROU 


PORC    AIN 


SOLI:  MAKERS  Or  I-X-L  CLEttTS 


riAIN  AND  BRANCH  CUT-OUTS 

CEILING  AND  MOULDING  IXXSCTTCS 

SWITCH  RASIlS  AND 

SOCKETS 

WALL  RECEPTACLES 
HANGER-I5OARD.S        SOCKET  BUTTONS 
INSUIJVrOPS 


SPECIAL  ATTENTION  GIVEN  TO 
PORCELAIN    SPECIALTIES 


orricr:  AND  WORKS 

TOENTON,  MEW  JERSEY,  tl.  5. 


192 


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WARD  &  Co. 


27 

THAMES  ST. 
NEW  YORK 


Contractors  for  the  Complete  Installation 
of  Electric  Light  and  Power  Plants,  in 
accordance  with  the  best  practice 


.  . THE . . 


«*• 

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«•  X 


IS  THE  OLDEST  AND  IS  THE  LEADING  PUBLICATION  «f» 
DEVOTED  TO  THE  SUBJECT  OF  ELECTRIC  AND  «£» 
STREET  RAILWAY  PRACTICE 


IT  COVERS 


THE   WHOLE  BROAD   FIELD   OF   ELECTRIC  TRACTION  THE  WORLD  X 

OVER,  AND  IS  THE  RECOGNIZED  AUTHORITY  ON  THIS  SUBJECT  .    .  T 

SUBSCRIPTIONS  :  United  States,  Canada  and  Mexico,  84.0O  per  year  «§* 

All  other  countries,  including  postage,  $6.OO  *§* 


Street  Railway  Publishing  Company 


A  Year  of  the  ... 


26  COPJTLA.NDT  ST. 
NEW  YORK 


Street  Railwap  journal 

makes  two  large  books  of  great 
practical  value  to  every  one  in- 
terested in  Street  Railways. 


HARB  RUBBER  ELECTRICAL? 


MANUFACTURED  BY 


The  Columbia  Rubber  Works  Co. 


66  AND  68  READE  STREET 


NEW  YORK 


FACTORIES  AT  AKRON,  OHIO 


195 


j  tl 


GENL.  INC.  ARC  LIGHT  CO. 
BUILDERS 


"THE   DAIKER" 

[APARTMENT  HOUSE] 

NEW  YORK  CITY 


N.  Y.  ELECTRIC  EQUIPMENT  CO. 
CONTRACTORS 


THE  SWITCHES  AND  SWITCHBOARDS 


...OF  THE... 


General  Incandescent  Arc  Light  Co. 


NEW  YORK 


ARE  THE  RECOGNIZED  STANDARDS  OF  EXCELLENCE  AND  WORKMANSHIP 

AND  ARE  LOW  IN  PRICE 


AS  EVIDENCED  BY  ANY  OF  THE  HUNDREDS  OF  SWITCHBOARDS  BUILT 
BY  THEM  AND  IN  USE  EVERYWHERE 

...Send  for  Catalogue... 

GENERAL  INCANDESCENT  ARC  LIGHT  CO. 

S.  BERGMANN,  President 

572-578  First  Avenue,  New  York 

CORNER  THIRTY-THIRD  STREET 

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J.  M.  7,rRN 


THE  O.  F.  ZURN  CO. 


J.  I).  KELI.EY 
C    J.  CURRAN 


High-Grade  Lubricating  Oils  and  Greases 

Particularly  suited  to  Electrical  Machinery.     If  you  have  Rope  Drives, 

write  for  sample  of  our  ROPOLEUfl,  the  best  Dressing 

known  for  Manilla,  Hemp  or  Cotton  Ropes 

408-418  VINE  STREET  PHILADELPHIA 

CARBONS—  Electric  Light   Carbons,   Soft  Cored    and  Solid,  Carbon  Brushes, 


Battery  Carbons 

SOLAR  CARBON  &  MFG.  CO. 

339  Fifth  Avenue,  Pittsburgh,  Pa. 

Manufacturers  of  EVERYTHING  IN  THE  CARBON  LINE 
Write  for  Prices 


We  are  PURCHASERS  of  the 
PLATINUM  contained  in  the  base  of 


BURNED-OUT   INCANDESCENT   LAMPS 

BAKER  &  CO.,  Newark,  N.  J. 


WRITE 


MANUFACTURERS  OF    PLATINUM     SHEET  OR  WIRE,  ANY  SIZE,  SHAPE 

OR  DEGREE  OF   HARDNESS,   FOR  ALL  PURPOSES 


REGJRADE MARKS  THE  PHOSPHOR  BRONZE  SMELTINGCO.QMITED, 
2200  WASHINGTON  AVE.,PHILADELPHIA. 
,  'ELEPHANT  BRAND  PHOSPHOR-BRONZE" 
INGOTS,CASTINGS,WIRE,RODS,SHEETS,Efc. 
3&a«£»U&«M>?  — DELTA  METAL  — 

S/l^.  CASTINGS,  STAMPINGS  AND  FORCINGS 

I         ORIGINAL  AND  SOLE  MAKERS  IN  THE  U.S. 


Delta 
fetal" 


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Built  by  W.  S.  Hill  Electric  Co. 


UTICA  STA  TE  HOSPITAL,  UTICA,  N.  Y. 


W.  S.  HILL  ELECTRIC  Co. 

NEW  BEDFORD,  MASS. 


BUILDERS  AND  DESIGNERS  OF 


Modern  Switchboards 

Some  of  our  recent  installments  include 

New  Public  Library,  Boston  Willard  State  Hospital,  Willard,  N.  Y. 

Post  Office,  Boston  Manhattan  State  Hospital,  Ward's  Island,  N.  Y. 

City  of  Boston  (4  Boards),  Boston  Long  Island  State  Hospital,   King's  Park,  N.  Y. 
Boston  Theatre,  Boston 

NOTE. — The  Switches  used  on  the  Switchboard  for  the  Congressional  Library, 
Washington,  D.  C.,  shown  on  opposite  page,  are  of  our  manufacture. 


201 


FRONT    AND    BACK    VIEWS   OF  BUILT  AND  INSTALLED  BY 

SIX-PANEL  RAILWAY  SWITCHBOARD  WALKER  co. 

CLEVELAND,  OHIO 


Special  European  Agent  for  the 


Cutter  Electrical  and  Mfg.  Co/s 
I-T-E  Circuit  Breakers 

WRITE  FOR  PRICES  AND  INFORMATION 

ROBERT  W.  BLACKWELL 

39  VICTORIA  STREET,  W. 
London,  England 


The  Crescent  Shade 


DIAMETER  10  INCHES 


This  Shade  is  made  of  Corru- 
gated Tin,  finished  in  brilliant 
green  enamel  outside,  and  pure 
white  enamel  inside.  The  enamel 
is  baked  on  and  will  not  flake  off 
or  crack. 

The  Shade  is  made  on  dies  af- 
ter our  own  design,  and  we  have 
spared  no  expense  to  make  it  the 
best  of  its  class,  and  to  sell  at  a 
price  no  higher  than  is  asked  for 
inferior  goods. 

NET  TRADE  PRICES 

Price  per  dozen,  $1.50 

Price  per  gross,  $15.00 

Special  price  for  larger  quantities. 


MANUFACTURED  BY 


BROS,  st  co. 


625   KRCH    STReeT 


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\|I:W  YORK  ELECTRIC 
EQUIPMENT  COMPANY 


S.   BERGMANN,  President  P.   H.   KLEIN,  JR.,  Treasurer 

OFFICES  AND  WORKS 

Cor.  33d  Street  and  First  Avenue 

TELEPHONE 
129-38111 

MAKE  A  SPECIALTY  OF  CARRYING  OUT  THE 
SPECIFICATIONS  OF  ARCHITECTS  AND  ELEC- 
TRICAL ENGINEERS  FOR  ALL  ELECTRICAL 
WORK,  THOROUGHLY  AND  CORRECTLY,  AND 
WITH  A  COMPETENT  AND  COMPLETELY 
EQUIPPED  ESTIMATING  DEPARTMENT,  FUR- 
NISHES ESTIMATES  WITH  THE  GREATEST 
PROMPTNESS  AND  ACCURACY  .-.  .-.  .-.  .-. 

REFERENCES 
LEADING    ARCHITECTS    AND    ELECTRICAL    ENGINEERS 


Agents  for 


"ftERGMANN"  !SG  ARC  LAMPS 


MANUFACTURED  BY  THE 


GENERAL  INCANDESCENT  KM.  LIGHT  COMPANY 


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The  Switchboard  shown  on  the  opposite  page  was  made  and  installed  by  us  at  the 

BOSTON  CITY  HOSPITAL 


WM.  J.  MURDOCK  &  CO 


MANUFACTURERS  OF 


SWITCHBOARDS 

No.    160   CONGRESS   STREET 

BOSTON,  MASS. 


We  will  be  pleased  to  furnish  plans  and  estimates 
of  Switchboards  for  electrical  purposes,  and  would 
solicit  your  correspondence. 

WM.  J.  MURDOCK  &  CO.,  160  Congress  Street,  Boston,  Mass. 

LONG  DISTANCE  TELEPHONE 

209 


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Two  Tablets  Worth  Reading 


Get  What  YOU  Fay  For 

You  advertise  to  get  results. 

Results  can  only  be  gotten  from 
a  paper  that  reaches  the  people 
who  buy,  or  who  counsel  buying. 

The  buyers  are  the  managers  of 
central  lighting  stations,  elec- 
tric railway  and  power  plants, 
supply  houses,  isolated  plants, 
telephone  exchanges,  etc. 

These  are  the  people  reached  by 
THE  ELECTRICAL  ENGINEER. 

QUANTITY  of  circulation  counts 
only  when  it  means  QUALITY  too. 

That  is  what  we  have — QUAN- 
TITY and  QUALITY,  and  that  is 
why  advertising  in  THE  ELEC. 
TRICAL  ENGINEER  pays. 

Weekly  Circulation,  10,000 


Moral 

Advertise 

Judiciously  and  Boldly  in 

THE  ELECTRICAL  ENGINEER 


Moral 

Read  constantly 

THE  ELECTRICAL  ENGINEER 

if  you  desire  to 

keep  abreast  of  the  times. 


Get  What  you  Fay  For 

You  read  electrical  papers  to 
get  news. 

To  get  news  you  want  to  know 
the  most  recent  practice  in  cen- 
tral station  design,  the  latest 
types  of  electric  generators,  mo- 
tors, dynamos,  telephones,  and 
all  kinds  of  electric  appliances. 

You  want  to  know  about  the 
great  electrical  projects  of  the 
day. 

You  want  to  know  the  latest 
electrical  supplies  on  the  market, 
so  that  whether  you  may  be  equip- 
ping your  own  plant,  or  trying  to 
sell  again,  you  are  at  least  posted. 

THE  ELECTRICAL  ENGINEER 

does  this  for  its  readers  m<  re 
thoroughly  than  any  other  elec- 
trical journal,  and  that  is  why  it 
is  the  most  widely  read. 

10  cents  a  cop}-,  $3.00  a  year. 

Weekly  Circulation,  10,000 


THE  ELECTRICAL  ENGINEER 

120  LIBERTY  STREET,  NEW  YORK 


211 


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SOME  OF  THE  PUBLICATIONS 

...  OF  ... 

THE  «.  J.  JOHNSTON  COMPANY. 


The  Electrical  World.  An  Illustrated  Weekly  Review  of 
Current  Progress  in  Electricity  and  its  Practical  Applications. 
Annual  subscription 83  00 

Dictionary  of  Electrical  AVords,  Terms  und   Phrases.    By 

Edwin  .1.  Houston,  Ph.D.  Fourth  edition.  Greatly  enlarged. 
10,042  words  and  terms  defined:  12,078  definition*;  990douhle- 
colntnii  octavo  pa-jes;  582  illustrations.  An  indispensable  ref- 
erence hook,  not  only  for  electricians,  but  for  every  one  in- 
terested in  current  progress $7.00 

Nliop   and   Koacl   Testing  of   Dynamos    and    Motors.     By 

Kuyrne  c.  Parhain  and  John  C.  Shedd.  Practical  and  thor- 
ough. 526  pages 82.00 

Klectro-Dynamic  Machinery.  By  E.  J.  Houston,  Ph.D.,  and 
A.  K.  Kennelly,  D.Sc.  A  text-book  on  continuous-current  dy- 
natno-electric  machinery  for  electric-engineering  students  of 
all  grades.  331  pages,  232  illustrations 82.50 

1'r  !<•(  i.  ;i  I  Calculation  of  Dynamo-Electric  Machines.  A 
.Manual  for  Electrical  and  Mechanical  Engineers,  and  a  Text- 
book for  Students  of  Eleclro-teclinics.  By  A.  E.  Wiener. 
683  pages,  375  illustrations 82.50 

Gerard's  Electricity.  With  chapters  by  Dr.  Louis  Duncan, 
('.  P.  Steinmelz,  A.  E.  Kennelly  and  Dr.  Gary  T.  Hutchin- 
sou.  Translated  under  the  direction  of  Dr.  Louis  Duncan.  JS92 
pages,  112  illustrations.  As  a  beautifully  clear  treatise  for  stu- 
dents on  the  theory  of  electricity  and  magnetism,  as  well  as  a 
resume  for  eiigineersof  electrical  theories  that  have  a  practical 
hearing,  the  work  of  Professor  Gerard  has  been  without  a 
rival  in  any  language 82. 50 

Klectrical  Power  Transmission.  By  Dr.  Louis  Bell,  Ph.D. 
rniform  with  Crosby  &  Bell's  "Electric  Railway."  Essen- 
tially practical  in  its  character.  Cloth 82.r,0 

The  Theory  and  Calculation  of  Alternating  Current  Phe- 
nomena. By  diaries  Proteus  Steinmetz.  Contains  the  very 
latest  knowledge  relating  to  alternate-current  phenomena, 
much  of  which  is  original  with  the  author,  and  here  appears 
for  the  first  time  in  book  form 82.50 

Central  Station  Bookkeeping.  With  Suggested  Forms.  By 
H.  A.  Foster 12.00 

Electric  Lighting  Specifications  for  the  use  of  Engineers  and 
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FAIRCHILD  &  SUMNER 


ST' 


.  GENERAL  AGENTS  FOR  . 


ONONDAGA  DYNAMO  CO.,  DIRAE^TASTRusENT 
THE  WARREN-MEDBERY  CO. 

Manufactures  of  u,e  IMPROVED  WARREN-ALTERNATING  GENERATOR 

217 


Imperial  Brass  Foundry 


LIMITED 


QEO.  H.  MOWERY,  Manager 


BRASS,  BRONZE,  COPPER 


.    . AND .    . 


WHITE    METAL 

ROUNDERS 

Castings  of  Red  and  Yellow  Brass,  Phosphor-Bronze,  White  Nickel  Metal  and 
Special  Metal  for  Patterns.     Fine  Castings  a  Specialty. 


Copper  Castings  of  very  high  conductivity 
Special  attention  given  to  Electrical  Work 


No.  119   SPRING  STREET 

(Formerly  Craven  Street) 
Above  Race,  between  Front  and  Second  Streets 

PHILADELPHIA 

218 


MERCHANT  &  Co., 

PHILADELPHIA         NEW  YORK         BROOKLYN         CHICAGO 


Inc. 


MANUFACTURERS  OF  AND  DEALERS  IN 


PURE  LAKE 
COPPER 


f    IN  COMMUTATOR  BARS, 

ROUND  RODS,  VARIOUS  SIZES 
RECTANGULAR  BARS  AND  ODD  SHAPES 


SWITCHBOARD  SHAPES  A  SPECIALTY 


SHEETS 


AND 


PLATES 


Brass 
Bronze 
Copper 
Zinc 


WIRE 


AND 


RODS 


GERMAN  SILVER  RESISTANCE  WIRE 
SPRING  BRUSH  COPPER 


Seamless  Drawn  Tubing  g 


Brass 
Bronze 

Copper 


Babbitt  and  Anti-Friction  Metals,  Solder,  Etc. 


219 


PATTISON  BROS. 
ELECTRICAL   ENGINEERS 


ST.  PAUL  BUILDING 
NEW  YORK  CITY 


CONTRACTORS 
N.  Y.  ELECTRIC  EQUIPMENT  CO. 


MR.  ROBERT  W.  BLACKWELL 

announces  that  he  has  opened  a  branch  office  in 

PARIS,  FRANCE 

No.  50  Boulevard  Haussmann 


TELEPHONE 


SIBLEY  &  PITMAN 


59  Duane  Street,  Corner  Elm  Street 
NEW  YORK  CITY 

Electric   Light  Supplies 

HOUSE   WIRING  SUPPLIES 

AGENTS   FOR  AGENTS   FOR 

PARTRICK,  CARTER  &  WILKINS      CONNECTICUT  TELEPHONE  CO. 


GENERAL  ELECTRIC  COMPANY'S  SUPPLIES 


ALFRED  F.  MOORE  CHARLES  C.  KING  ANTOINE  BOURNONV1LLE 

Established  1820 

ALFRED  F.  MOORE 

MANUFACTURER  OF 

Insulated  Electric  Wire,  Flexible  Cords  and  Cables 

200  NORTH  THIRD  STREET 

PHILADELPHIA,  PA. 

221 


HOUSE  GOODS 

OUR  SPECIALTY 


1867  1898 

Partriek,  Garter  &  Wilkins 


and  Dealers 

125  South  Second  Street 
Philadelphia 


GENERAL  SUPPLIES 

OF  ALL  KINDS 


222 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN  INITIAL  PINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  S1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


13  1937 


OCT  12  1939 


LD  21-95m-7,'37 


YE  01956 


